\chapter{Concrete Objects Layer \label{concrete}} The functions in this chapter are specific to certain Python object types. Passing them an object of the wrong type is not a good idea; if you receive an object from a Python program and you are not sure that it has the right type, you must perform a type check first; for example, to check that an object is a dictionary, use \cfunction{PyDict_Check()}. The chapter is structured like the ``family tree'' of Python object types. \warning{While the functions described in this chapter carefully check the type of the objects which are passed in, many of them do not check for \NULL{} being passed instead of a valid object. Allowing \NULL{} to be passed in can cause memory access violations and immediate termination of the interpreter.} \section{Fundamental Objects \label{fundamental}} This section describes Python type objects and the singleton object \code{None}. \subsection{Type Objects \label{typeObjects}} \obindex{type} \begin{ctypedesc}{PyTypeObject} The C structure of the objects used to describe built-in types. \end{ctypedesc} \begin{cvardesc}{PyObject*}{PyType_Type} This is the type object for type objects; it is the same object as \code{types.TypeType} in the Python layer. \withsubitem{(in module types)}{\ttindex{TypeType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyType_Check}{PyObject *o} Returns true if the object \var{o} is a type object, including instances of types derived from the standard type object. Returns false in all other cases. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyType_CheckExact}{PyObject *o} Returns true if the object \var{o} is a type object, but not a subtype of the standard type object. Returns false in all other cases. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyType_HasFeature}{PyObject *o, int feature} Returns true if the type object \var{o} sets the feature \var{feature}. Type features are denoted by single bit flags. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyType_IS_GC}{PyObject *o} Return true if the type object includes support for the cycle detector; this tests the type flag \constant{Py_TPFLAGS_HAVE_GC}. \versionadded{2.0} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyType_IsSubtype}{PyTypeObject *a, PyTypeObject *b} Returns true if \var{a} is a subtype of \var{b}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyType_GenericAlloc}{PyTypeObject *type, int nitems} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyType_GenericNew}{PyTypeObject *type, PyObject *args, PyObject *kwds} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyType_Ready}{PyTypeObject *type} Finalize a type object. This should be called on all type objects to finish their initialization. This function is responsible for adding inherited slots from a type's base class. Returns \code{0} on success, or returns \code{-1} and sets an exception on error. \versionadded{2.2} \end{cfuncdesc} \subsection{The None Object \label{noneObject}} \obindex{None@\texttt{None}} Note that the \ctype{PyTypeObject} for \code{None} is not directly exposed in the Python/C API. Since \code{None} is a singleton, testing for object identity (using \samp{==} in C) is sufficient. There is no \cfunction{PyNone_Check()} function for the same reason. \begin{cvardesc}{PyObject*}{Py_None} The Python \code{None} object, denoting lack of value. This object has no methods. It needs to be treated just like any other object with respect to reference counts. \end{cvardesc} \section{Numeric Objects \label{numericObjects}} \obindex{numeric} \subsection{Plain Integer Objects \label{intObjects}} \obindex{integer} \begin{ctypedesc}{PyIntObject} This subtype of \ctype{PyObject} represents a Python integer object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyInt_Type} This instance of \ctype{PyTypeObject} represents the Python plain integer type. This is the same object as \code{types.IntType}. \withsubitem{(in modules types)}{\ttindex{IntType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyInt_Check}{PyObject* o} Returns true if \var{o} is of type \cdata{PyInt_Type} or a subtype of \cdata{PyInt_Type}. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyInt_CheckExact}{PyObject* o} Returns true if \var{o} is of type \cdata{PyInt_Type}, but not a subtype of \cdata{PyInt_Type}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyInt_FromString}{char *str, char **pend, int base} Return a new \ctype{PyIntObject} or \ctype{PyLongObject} based on the string value in \var{str}, which is interpreted according to the radix in \var{base}. If \var{pend} is non-\NULL, \code{*\var{pend}} will point to the first character in \var{str} which follows the representation of the number. If \var{base} is \code{0}, the radix will be determined based on the leading characters of \var{str}: if \var{str} starts with \code{'0x'} or \code{'0X'}, radix 16 will be used; if \var{str} starts with \code{'0'}, radix 8 will be used; otherwise radix 10 will be used. If \var{base} is not \code{0}, it must be between \code{2} and \code{36}, inclusive. Leading spaces are ignored. If there are no digits, \exception{ValueError} will be raised. If the string represents a number too large to be contained within the machine's \ctype{long int} type and overflow warnings are being suppressed, a \ctype{PyLongObject} will be returned. If overflow warnings are not being suppressed, \NULL{} will be returned in this case. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyInt_FromLong}{long ival} Creates a new integer object with a value of \var{ival}. The current implementation keeps an array of integer objects for all integers between \code{-1} and \code{100}, when you create an int in that range you actually just get back a reference to the existing object. So it should be possible to change the value of \code{1}. I suspect the behaviour of Python in this case is undefined. :-) \end{cfuncdesc} \begin{cfuncdesc}{long}{PyInt_AsLong}{PyObject *io} Will first attempt to cast the object to a \ctype{PyIntObject}, if it is not already one, and then return its value. \end{cfuncdesc} \begin{cfuncdesc}{long}{PyInt_AS_LONG}{PyObject *io} Returns the value of the object \var{io}. No error checking is performed. \end{cfuncdesc} \begin{cfuncdesc}{long}{PyInt_GetMax}{} Returns the system's idea of the largest integer it can handle (\constant{LONG_MAX}\ttindex{LONG_MAX}, as defined in the system header files). \end{cfuncdesc} \subsection{Long Integer Objects \label{longObjects}} \obindex{long integer} \begin{ctypedesc}{PyLongObject} This subtype of \ctype{PyObject} represents a Python long integer object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyLong_Type} This instance of \ctype{PyTypeObject} represents the Python long integer type. This is the same object as \code{types.LongType}. \withsubitem{(in modules types)}{\ttindex{LongType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyLong_Check}{PyObject *p} Returns true if its argument is a \ctype{PyLongObject} or a subtype of \ctype{PyLongObject}. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyLong_CheckExact}{PyObject *p} Returns true if its argument is a \ctype{PyLongObject}, but not a subtype of \ctype{PyLongObject}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromLong}{long v} Returns a new \ctype{PyLongObject} object from \var{v}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromUnsignedLong}{unsigned long v} Returns a new \ctype{PyLongObject} object from a C \ctype{unsigned long}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromLongLong}{long long v} Returns a new \ctype{PyLongObject} object from a C \ctype{long long}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromUnsignedLongLong}{unsigned long long v} Returns a new \ctype{PyLongObject} object from a C \ctype{unsigned long long}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromDouble}{double v} Returns a new \ctype{PyLongObject} object from the integer part of \var{v}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromString}{char *str, char **pend, int base} Return a new \ctype{PyLongObject} based on the string value in \var{str}, which is interpreted according to the radix in \var{base}. If \var{pend} is non-\NULL, \code{*\var{pend}} will point to the first character in \var{str} which follows the representation of the number. If \var{base} is \code{0}, the radix will be determined based on the leading characters of \var{str}: if \var{str} starts with \code{'0x'} or \code{'0X'}, radix 16 will be used; if \var{str} starts with \code{'0'}, radix 8 will be used; otherwise radix 10 will be used. If \var{base} is not \code{0}, it must be between \code{2} and \code{36}, inclusive. Leading spaces are ignored. If there are no digits, \exception{ValueError} will be raised. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromUnicode}{Py_UNICODE *u, int length, int base} Convert a sequence of Unicode digits to a Python long integer value. The first parameter, \var{u}, points to the first character of the Unicode string, \var{length} gives the number of characters, and \var{base} is the radix for the conversion. The radix must be in the range [2, 36]; if it is out of range, \exception{ValueError} will be raised. \versionadded{1.6} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyLong_FromVoidPtr}{void *p} Create a Python integer or long integer from the pointer \var{p}. The pointer value can be retrieved from the resulting value using \cfunction{PyLong_AsVoidPtr()}. \versionadded{1.5.2} \end{cfuncdesc} \begin{cfuncdesc}{long}{PyLong_AsLong}{PyObject *pylong} Returns a C \ctype{long} representation of the contents of \var{pylong}. If \var{pylong} is greater than \constant{LONG_MAX}\ttindex{LONG_MAX}, an \exception{OverflowError} is raised. \withsubitem{(built-in exception)}{\ttindex{OverflowError}} \end{cfuncdesc} \begin{cfuncdesc}{unsigned long}{PyLong_AsUnsignedLong}{PyObject *pylong} Returns a C \ctype{unsigned long} representation of the contents of \var{pylong}. If \var{pylong} is greater than \constant{ULONG_MAX}\ttindex{ULONG_MAX}, an \exception{OverflowError} is raised. \withsubitem{(built-in exception)}{\ttindex{OverflowError}} \end{cfuncdesc} \begin{cfuncdesc}{long long}{PyLong_AsLongLong}{PyObject *pylong} Return a C \ctype{long long} from a Python long integer. If \var{pylong} cannot be represented as a \ctype{long long}, an \exception{OverflowError} will be raised. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{unsigned long long}{PyLong_AsUnsignedLongLong}{PyObject *pylong} Return a C \ctype{unsigned long long} from a Python long integer. If \var{pylong} cannot be represented as an \ctype{unsigned long long}, an \exception{OverflowError} will be raised if the value is positive, or a \exception{TypeError} will be raised if the value is negative. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{double}{PyLong_AsDouble}{PyObject *pylong} Returns a C \ctype{double} representation of the contents of \var{pylong}. If \var{pylong} cannot be approximately represented as a \ctype{double}, an \exception{OverflowError} exception is raised and \code{-1.0} will be returned. \end{cfuncdesc} \begin{cfuncdesc}{void*}{PyLong_AsVoidPtr}{PyObject *pylong} Convert a Python integer or long integer \var{pylong} to a C \ctype{void} pointer. If \var{pylong} cannot be converted, an \exception{OverflowError} will be raised. This is only assured to produce a usable \ctype{void} pointer for values created with \cfunction{PyLong_FromVoidPtr()}. \versionadded{1.5.2} \end{cfuncdesc} \subsection{Floating Point Objects \label{floatObjects}} \obindex{floating point} \begin{ctypedesc}{PyFloatObject} This subtype of \ctype{PyObject} represents a Python floating point object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyFloat_Type} This instance of \ctype{PyTypeObject} represents the Python floating point type. This is the same object as \code{types.FloatType}. \withsubitem{(in modules types)}{\ttindex{FloatType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyFloat_Check}{PyObject *p} Returns true if its argument is a \ctype{PyFloatObject} or a subtype of \ctype{PyFloatObject}. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyFloat_CheckExact}{PyObject *p} Returns true if its argument is a \ctype{PyFloatObject}, but not a subtype of \ctype{PyFloatObject}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFloat_FromString}{PyObject *str, char **pend} Creates a \ctype{PyFloatObject} object based on the string value in \var{str}, or \NULL{} on failure. The \var{pend} argument is ignored. It remains only for backward compatibility. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFloat_FromDouble}{double v} Creates a \ctype{PyFloatObject} object from \var{v}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{double}{PyFloat_AsDouble}{PyObject *pyfloat} Returns a C \ctype{double} representation of the contents of \var{pyfloat}. \end{cfuncdesc} \begin{cfuncdesc}{double}{PyFloat_AS_DOUBLE}{PyObject *pyfloat} Returns a C \ctype{double} representation of the contents of \var{pyfloat}, but without error checking. \end{cfuncdesc} \subsection{Complex Number Objects \label{complexObjects}} \obindex{complex number} Python's complex number objects are implemented as two distinct types when viewed from the C API: one is the Python object exposed to Python programs, and the other is a C structure which represents the actual complex number value. The API provides functions for working with both. \subsubsection{Complex Numbers as C Structures} Note that the functions which accept these structures as parameters and return them as results do so \emph{by value} rather than dereferencing them through pointers. This is consistent throughout the API. \begin{ctypedesc}{Py_complex} The C structure which corresponds to the value portion of a Python complex number object. Most of the functions for dealing with complex number objects use structures of this type as input or output values, as appropriate. It is defined as: \begin{verbatim} typedef struct { double real; double imag; } Py_complex; \end{verbatim} \end{ctypedesc} \begin{cfuncdesc}{Py_complex}{_Py_c_sum}{Py_complex left, Py_complex right} Return the sum of two complex numbers, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{_Py_c_diff}{Py_complex left, Py_complex right} Return the difference between two complex numbers, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{_Py_c_neg}{Py_complex complex} Return the negation of the complex number \var{complex}, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{_Py_c_prod}{Py_complex left, Py_complex right} Return the product of two complex numbers, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{_Py_c_quot}{Py_complex dividend, Py_complex divisor} Return the quotient of two complex numbers, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{_Py_c_pow}{Py_complex num, Py_complex exp} Return the exponentiation of \var{num} by \var{exp}, using the C \ctype{Py_complex} representation. \end{cfuncdesc} \subsubsection{Complex Numbers as Python Objects} \begin{ctypedesc}{PyComplexObject} This subtype of \ctype{PyObject} represents a Python complex number object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyComplex_Type} This instance of \ctype{PyTypeObject} represents the Python complex number type. \end{cvardesc} \begin{cfuncdesc}{int}{PyComplex_Check}{PyObject *p} Returns true if its argument is a \ctype{PyComplexObject} or a subtype of \ctype{PyComplexObject}. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyComplex_CheckExact}{PyObject *p} Returns true if its argument is a \ctype{PyComplexObject}, but not a subtype of \ctype{PyComplexObject}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyComplex_FromCComplex}{Py_complex v} Create a new Python complex number object from a C \ctype{Py_complex} value. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyComplex_FromDoubles}{double real, double imag} Returns a new \ctype{PyComplexObject} object from \var{real} and \var{imag}. \end{cfuncdesc} \begin{cfuncdesc}{double}{PyComplex_RealAsDouble}{PyObject *op} Returns the real part of \var{op} as a C \ctype{double}. \end{cfuncdesc} \begin{cfuncdesc}{double}{PyComplex_ImagAsDouble}{PyObject *op} Returns the imaginary part of \var{op} as a C \ctype{double}. \end{cfuncdesc} \begin{cfuncdesc}{Py_complex}{PyComplex_AsCComplex}{PyObject *op} Returns the \ctype{Py_complex} value of the complex number \var{op}. \end{cfuncdesc} \section{Sequence Objects \label{sequenceObjects}} \obindex{sequence} Generic operations on sequence objects were discussed in the previous chapter; this section deals with the specific kinds of sequence objects that are intrinsic to the Python language. \subsection{String Objects \label{stringObjects}} These functions raise \exception{TypeError} when expecting a string parameter and are called with a non-string parameter. \obindex{string} \begin{ctypedesc}{PyStringObject} This subtype of \ctype{PyObject} represents a Python string object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyString_Type} This instance of \ctype{PyTypeObject} represents the Python string type; it is the same object as \code{types.TypeType} in the Python layer. \withsubitem{(in module types)}{\ttindex{StringType}}. \end{cvardesc} \begin{cfuncdesc}{int}{PyString_Check}{PyObject *o} Returns true if the object \var{o} is a string object or an instance of a subtype of the string type. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyString_CheckExact}{PyObject *o} Returns true if the object \var{o} is a string object, but not an instance of a subtype of the string type. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_FromString}{const char *v} Returns a new string object with the value \var{v} on success, and \NULL{} on failure. The parameter \var{v} must not be \NULL; it will not be checked. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_FromStringAndSize}{const char *v, int len} Returns a new string object with the value \var{v} and length \var{len} on success, and \NULL{} on failure. If \var{v} is \NULL, the contents of the string are uninitialized. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_FromFormat}{const char *format, ...} Takes a C \cfunction{printf()}-style \var{format} string and a variable number of arguments, calculates the size of the resulting Python string and returns a string with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the \var{format} string. The following format characters are allowed: \begin{tableiii}{l|l|l}{member}{Format Characters}{Type}{Comment} \lineiii{\%\%}{\emph{n/a}}{The literal \% character.} \lineiii{\%c}{int}{A single character, represented as an C int.} \lineiii{\%d}{int}{Exactly equivalent to \code{printf("\%d")}.} \lineiii{\%ld}{long}{Exactly equivalent to \code{printf("\%ld")}.} \lineiii{\%i}{int}{Exactly equivalent to \code{printf("\%i")}.} \lineiii{\%x}{int}{Exactly equivalent to \code{printf("\%x")}.} \lineiii{\%s}{char*}{A null-terminated C character array.} \lineiii{\%p}{void*}{The hex representation of a C pointer. Mostly equivalent to \code{printf("\%p")} except that it is guaranteed to start with the literal \code{0x} regardless of what the platform's \code{printf} yields.} \end{tableiii} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_FromFormatV}{const char *format, va_list vargs} Identical to \function{PyString_FromFormat()} except that it takes exactly two arguments. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyString_Size}{PyObject *string} Returns the length of the string in string object \var{string}. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyString_GET_SIZE}{PyObject *string} Macro form of \cfunction{PyString_Size()} but without error checking. \end{cfuncdesc} \begin{cfuncdesc}{char*}{PyString_AsString}{PyObject *string} Returns a NUL-terminated representation of the contents of \var{string}. The pointer refers to the internal buffer of \var{string}, not a copy. The data must not be modified in any way, unless the string was just created using \code{PyString_FromStringAndSize(NULL, \var{size})}. It must not be deallocated. If \var{string} is a Unicode object, this function computes the default encoding of \var{string} and operates on that. If \var{string} is not a string object at all, \cfunction{PyString_AsString()} returns \NULL{} and raises \exception{TypeError}. \end{cfuncdesc} \begin{cfuncdesc}{char*}{PyString_AS_STRING}{PyObject *string} Macro form of \cfunction{PyString_AsString()} but without error checking. Only string objects are supported; no Unicode objects should be passed. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyString_AsStringAndSize}{PyObject *obj, char **buffer, int *length} Returns a NUL-terminated representation of the contents of the object \var{obj} through the output variables \var{buffer} and \var{length}. The function accepts both string and Unicode objects as input. For Unicode objects it returns the default encoded version of the object. If \var{length} is \NULL, the resulting buffer may not contain NUL characters; if it does, the function returns \code{-1} and a \exception{TypeError} is raised. The buffer refers to an internal string buffer of \var{obj}, not a copy. The data must not be modified in any way, unless the string was just created using \code{PyString_FromStringAndSize(NULL, \var{size})}. It must not be deallocated. If \var{string} is a Unicode object, this function computes the default encoding of \var{string} and operates on that. If \var{string} is not a string object at all, \cfunction{PyString_AsString()} returns \NULL{} and raises \exception{TypeError}. \end{cfuncdesc} \begin{cfuncdesc}{void}{PyString_Concat}{PyObject **string, PyObject *newpart} Creates a new string object in \var{*string} containing the contents of \var{newpart} appended to \var{string}; the caller will own the new reference. The reference to the old value of \var{string} will be stolen. If the new string cannot be created, the old reference to \var{string} will still be discarded and the value of \var{*string} will be set to \NULL; the appropriate exception will be set. \end{cfuncdesc} \begin{cfuncdesc}{void}{PyString_ConcatAndDel}{PyObject **string, PyObject *newpart} Creates a new string object in \var{*string} containing the contents of \var{newpart} appended to \var{string}. This version decrements the reference count of \var{newpart}. \end{cfuncdesc} \begin{cfuncdesc}{int}{_PyString_Resize}{PyObject **string, int newsize} A way to resize a string object even though it is ``immutable''. Only use this to build up a brand new string object; don't use this if the string may already be known in other parts of the code. It is an error to call this function if the refcount on the input string object is not one. Pass the address of an existing string object as an lvalue (it may be written into), and the new size desired. On success, \var{*string} holds the resized string object and \code{0} is returned; the address in \var{*string} may differ from its input value. If the reallocation fails, the original string object at \var{*string} is deallocated, \var{*string} is set to \NULL{}, a memory exception is set, and \code{-1} is returned. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_Format}{PyObject *format, PyObject *args} Returns a new string object from \var{format} and \var{args}. Analogous to \code{\var{format} \%\ \var{args}}. The \var{args} argument must be a tuple. \end{cfuncdesc} \begin{cfuncdesc}{void}{PyString_InternInPlace}{PyObject **string} Intern the argument \var{*string} in place. The argument must be the address of a pointer variable pointing to a Python string object. If there is an existing interned string that is the same as \var{*string}, it sets \var{*string} to it (decrementing the reference count of the old string object and incrementing the reference count of the interned string object), otherwise it leaves \var{*string} alone and interns it (incrementing its reference count). (Clarification: even though there is a lot of talk about reference counts, think of this function as reference-count-neutral; you own the object after the call if and only if you owned it before the call.) \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_InternFromString}{const char *v} A combination of \cfunction{PyString_FromString()} and \cfunction{PyString_InternInPlace()}, returning either a new string object that has been interned, or a new (``owned'') reference to an earlier interned string object with the same value. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_Decode}{const char *s, int size, const char *encoding, const char *errors} Creates an object by decoding \var{size} bytes of the encoded buffer \var{s} using the codec registered for \var{encoding}. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the \function{unicode()} built-in function. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_AsDecodedObject}{PyObject *str, const char *encoding, const char *errors} Decodes a string object by passing it to the codec registered for \var{encoding} and returns the result as Python object. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the string \method{encode()} method. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_Encode}{const char *s, int size, const char *encoding, const char *errors} Encodes the \ctype{char} buffer of the given size by passing it to the codec registered for \var{encoding} and returns a Python object. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the string \method{encode()} method. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyString_AsEncodedObject}{PyObject *str, const char *encoding, const char *errors} Encodes a string object using the codec registered for \var{encoding} and returns the result as Python object. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the string \method{encode()} method. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \subsection{Unicode Objects \label{unicodeObjects}} \sectionauthor{Marc-Andre Lemburg}{mal@lemburg.com} %--- Unicode Type ------------------------------------------------------- These are the basic Unicode object types used for the Unicode implementation in Python: \begin{ctypedesc}{Py_UNICODE} This type represents a 16-bit unsigned storage type which is used by Python internally as basis for holding Unicode ordinals. On platforms where \ctype{wchar_t} is available and also has 16-bits, \ctype{Py_UNICODE} is a typedef alias for \ctype{wchar_t} to enhance native platform compatibility. On all other platforms, \ctype{Py_UNICODE} is a typedef alias for \ctype{unsigned short}. \end{ctypedesc} \begin{ctypedesc}{PyUnicodeObject} This subtype of \ctype{PyObject} represents a Python Unicode object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyUnicode_Type} This instance of \ctype{PyTypeObject} represents the Python Unicode type. \end{cvardesc} The following APIs are really C macros and can be used to do fast checks and to access internal read-only data of Unicode objects: \begin{cfuncdesc}{int}{PyUnicode_Check}{PyObject *o} Returns true if the object \var{o} is a Unicode object or an instance of a Unicode subtype. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_CheckExact}{PyObject *o} Returns true if the object \var{o} is a Unicode object, but not an instance of a subtype. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_GET_SIZE}{PyObject *o} Returns the size of the object. \var{o} has to be a \ctype{PyUnicodeObject} (not checked). \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_GET_DATA_SIZE}{PyObject *o} Returns the size of the object's internal buffer in bytes. \var{o} has to be a \ctype{PyUnicodeObject} (not checked). \end{cfuncdesc} \begin{cfuncdesc}{Py_UNICODE*}{PyUnicode_AS_UNICODE}{PyObject *o} Returns a pointer to the internal \ctype{Py_UNICODE} buffer of the object. \var{o} has to be a \ctype{PyUnicodeObject} (not checked). \end{cfuncdesc} \begin{cfuncdesc}{const char*}{PyUnicode_AS_DATA}{PyObject *o} Returns a pointer to the internal buffer of the object. \var{o} has to be a \ctype{PyUnicodeObject} (not checked). \end{cfuncdesc} % --- Unicode character properties --------------------------------------- Unicode provides many different character properties. The most often needed ones are available through these macros which are mapped to C functions depending on the Python configuration. \begin{cfuncdesc}{int}{Py_UNICODE_ISSPACE}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a whitespace character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISLOWER}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a lowercase character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISUPPER}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is an uppercase character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISTITLE}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a titlecase character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISLINEBREAK}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a linebreak character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISDECIMAL}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a decimal character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISDIGIT}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a digit character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISNUMERIC}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is a numeric character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISALPHA}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is an alphabetic character. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_ISALNUM}{Py_UNICODE ch} Returns 1/0 depending on whether \var{ch} is an alphanumeric character. \end{cfuncdesc} These APIs can be used for fast direct character conversions: \begin{cfuncdesc}{Py_UNICODE}{Py_UNICODE_TOLOWER}{Py_UNICODE ch} Returns the character \var{ch} converted to lower case. \end{cfuncdesc} \begin{cfuncdesc}{Py_UNICODE}{Py_UNICODE_TOUPPER}{Py_UNICODE ch} Returns the character \var{ch} converted to upper case. \end{cfuncdesc} \begin{cfuncdesc}{Py_UNICODE}{Py_UNICODE_TOTITLE}{Py_UNICODE ch} Returns the character \var{ch} converted to title case. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_TODECIMAL}{Py_UNICODE ch} Returns the character \var{ch} converted to a decimal positive integer. Returns \code{-1} if this is not possible. Does not raise exceptions. \end{cfuncdesc} \begin{cfuncdesc}{int}{Py_UNICODE_TODIGIT}{Py_UNICODE ch} Returns the character \var{ch} converted to a single digit integer. Returns \code{-1} if this is not possible. Does not raise exceptions. \end{cfuncdesc} \begin{cfuncdesc}{double}{Py_UNICODE_TONUMERIC}{Py_UNICODE ch} Returns the character \var{ch} converted to a (positive) double. Returns \code{-1.0} if this is not possible. Does not raise exceptions. \end{cfuncdesc} % --- Plain Py_UNICODE --------------------------------------------------- To create Unicode objects and access their basic sequence properties, use these APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_FromUnicode}{const Py_UNICODE *u, int size} Create a Unicode Object from the Py_UNICODE buffer \var{u} of the given size. \var{u} may be \NULL{} which causes the contents to be undefined. It is the user's responsibility to fill in the needed data. The buffer is copied into the new object. If the buffer is not \NULL, the return value might be a shared object. Therefore, modification of the resulting Unicode object is only allowed when \var{u} is \NULL. \end{cfuncdesc} \begin{cfuncdesc}{Py_UNICODE*}{PyUnicode_AsUnicode}{PyObject *unicode} Return a read-only pointer to the Unicode object's internal \ctype{Py_UNICODE} buffer, \NULL{} if \var{unicode} is not a Unicode object. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_GetSize}{PyObject *unicode} Return the length of the Unicode object. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_FromEncodedObject}{PyObject *obj, const char *encoding, const char *errors} Coerce an encoded object \var{obj} to an Unicode object and return a reference with incremented refcount. Coercion is done in the following way: \begin{enumerate} \item Unicode objects are passed back as-is with incremented refcount. \note{These cannot be decoded; passing a non-\NULL{} value for encoding will result in a \exception{TypeError}.} \item String and other char buffer compatible objects are decoded according to the given encoding and using the error handling defined by errors. Both can be \NULL{} to have the interface use the default values (see the next section for details). \item All other objects cause an exception. \end{enumerate} The API returns \NULL{} if there was an error. The caller is responsible for decref'ing the returned objects. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_FromObject}{PyObject *obj} Shortcut for \code{PyUnicode_FromEncodedObject(obj, NULL, "strict")} which is used throughout the interpreter whenever coercion to Unicode is needed. \end{cfuncdesc} % --- wchar_t support for platforms which support it --------------------- If the platform supports \ctype{wchar_t} and provides a header file wchar.h, Python can interface directly to this type using the following functions. Support is optimized if Python's own \ctype{Py_UNICODE} type is identical to the system's \ctype{wchar_t}. \begin{cfuncdesc}{PyObject*}{PyUnicode_FromWideChar}{const wchar_t *w, int size} Create a Unicode object from the \ctype{wchar_t} buffer \var{w} of the given size. Returns \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_AsWideChar}{PyUnicodeObject *unicode, wchar_t *w, int size} Copies the Unicode object contents into the \ctype{wchar_t} buffer \var{w}. At most \var{size} \ctype{wchar_t} characters are copied. Returns the number of \ctype{wchar_t} characters copied or -1 in case of an error. \end{cfuncdesc} \subsubsection{Built-in Codecs \label{builtinCodecs}} Python provides a set of builtin codecs which are written in C for speed. All of these codecs are directly usable via the following functions. Many of the following APIs take two arguments encoding and errors. These parameters encoding and errors have the same semantics as the ones of the builtin unicode() Unicode object constructor. Setting encoding to \NULL{} causes the default encoding to be used which is \ASCII. The file system calls should use \cdata{Py_FileSystemDefaultEncoding} as the encoding for file names. This variable should be treated as read-only: On some systems, it will be a pointer to a static string, on others, it will change at run-time, e.g. when the application invokes setlocale. Error handling is set by errors which may also be set to \NULL{} meaning to use the default handling defined for the codec. Default error handling for all builtin codecs is ``strict'' (\exception{ValueError} is raised). The codecs all use a similar interface. Only deviation from the following generic ones are documented for simplicity. % --- Generic Codecs ----------------------------------------------------- These are the generic codec APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_Decode}{const char *s, int size, const char *encoding, const char *errors} Create a Unicode object by decoding \var{size} bytes of the encoded string \var{s}. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the \function{unicode()} builtin function. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Encode}{const Py_UNICODE *s, int size, const char *encoding, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size and returns a Python string object. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the Unicode \method{encode()} method. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsEncodedString}{PyObject *unicode, const char *encoding, const char *errors} Encodes a Unicode object and returns the result as Python string object. \var{encoding} and \var{errors} have the same meaning as the parameters of the same name in the Unicode \method{encode()} method. The codec to be used is looked up using the Python codec registry. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- UTF-8 Codecs ------------------------------------------------------- These are the UTF-8 codec APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeUTF8}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the UTF-8 encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeUTF8}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using UTF-8 and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsUTF8String}{PyObject *unicode} Encodes a Unicode objects using UTF-8 and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- UTF-16 Codecs ------------------------------------------------------ */ These are the UTF-16 codec APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeUTF16}{const char *s, int size, const char *errors, int *byteorder} Decodes \var{length} bytes from a UTF-16 encoded buffer string and returns the corresponding Unicode object. \var{errors} (if non-\NULL) defines the error handling. It defaults to ``strict''. If \var{byteorder} is non-\NULL, the decoder starts decoding using the given byte order: \begin{verbatim} *byteorder == -1: little endian *byteorder == 0: native order *byteorder == 1: big endian \end{verbatim} and then switches according to all byte order marks (BOM) it finds in the input data. BOMs are not copied into the resulting Unicode string. After completion, \var{*byteorder} is set to the current byte order at the end of input data. If \var{byteorder} is \NULL, the codec starts in native order mode. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeUTF16}{const Py_UNICODE *s, int size, const char *errors, int byteorder} Returns a Python string object holding the UTF-16 encoded value of the Unicode data in \var{s}. If \var{byteorder} is not \code{0}, output is written according to the following byte order: \begin{verbatim} byteorder == -1: little endian byteorder == 0: native byte order (writes a BOM mark) byteorder == 1: big endian \end{verbatim} If byteorder is \code{0}, the output string will always start with the Unicode BOM mark (U+FEFF). In the other two modes, no BOM mark is prepended. Note that \ctype{Py_UNICODE} data is being interpreted as UTF-16 reduced to UCS-2. This trick makes it possible to add full UTF-16 capabilities at a later point without comprimising the APIs. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsUTF16String}{PyObject *unicode} Returns a Python string using the UTF-16 encoding in native byte order. The string always starts with a BOM mark. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- Unicode-Escape Codecs ---------------------------------------------- These are the ``Unicode Esacpe'' codec APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeUnicodeEscape}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the Unicode-Escape encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeUnicodeEscape}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using Unicode-Escape and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsUnicodeEscapeString}{PyObject *unicode} Encodes a Unicode objects using Unicode-Escape and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- Raw-Unicode-Escape Codecs ------------------------------------------ These are the ``Raw Unicode Esacpe'' codec APIs: \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeRawUnicodeEscape}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the Raw-Unicode-Esacpe encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeRawUnicodeEscape}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using Raw-Unicode-Escape and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsRawUnicodeEscapeString}{PyObject *unicode} Encodes a Unicode objects using Raw-Unicode-Escape and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- Latin-1 Codecs ----------------------------------------------------- These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256 Unicode ordinals and only these are accepted by the codecs during encoding. \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeLatin1}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the Latin-1 encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeLatin1}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using Latin-1 and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsLatin1String}{PyObject *unicode} Encodes a Unicode objects using Latin-1 and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- ASCII Codecs ------------------------------------------------------- These are the \ASCII{} codec APIs. Only 7-bit \ASCII{} data is accepted. All other codes generate errors. \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeASCII}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the \ASCII{} encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeASCII}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using \ASCII{} and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsASCIIString}{PyObject *unicode} Encodes a Unicode objects using \ASCII{} and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- Character Map Codecs ----------------------------------------------- These are the mapping codec APIs: This codec is special in that it can be used to implement many different codecs (and this is in fact what was done to obtain most of the standard codecs included in the \module{encodings} package). The codec uses mapping to encode and decode characters. Decoding mappings must map single string characters to single Unicode characters, integers (which are then interpreted as Unicode ordinals) or None (meaning "undefined mapping" and causing an error). Encoding mappings must map single Unicode characters to single string characters, integers (which are then interpreted as Latin-1 ordinals) or None (meaning "undefined mapping" and causing an error). The mapping objects provided must only support the __getitem__ mapping interface. If a character lookup fails with a LookupError, the character is copied as-is meaning that its ordinal value will be interpreted as Unicode or Latin-1 ordinal resp. Because of this, mappings only need to contain those mappings which map characters to different code points. \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeCharmap}{const char *s, int size, PyObject *mapping, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the encoded string \var{s} using the given \var{mapping} object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeCharmap}{const Py_UNICODE *s, int size, PyObject *mapping, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using the given \var{mapping} object and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsCharmapString}{PyObject *unicode, PyObject *mapping} Encodes a Unicode objects using the given \var{mapping} object and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} The following codec API is special in that maps Unicode to Unicode. \begin{cfuncdesc}{PyObject*}{PyUnicode_TranslateCharmap}{const Py_UNICODE *s, int size, PyObject *table, const char *errors} Translates a \ctype{Py_UNICODE} buffer of the given length by applying a character mapping \var{table} to it and returns the resulting Unicode object. Returns \NULL{} when an exception was raised by the codec. The \var{mapping} table must map Unicode ordinal integers to Unicode ordinal integers or None (causing deletion of the character). Mapping tables need only provide the method{__getitem__()} interface; dictionaries and sequences work well. Unmapped character ordinals (ones which cause a \exception{LookupError}) are left untouched and are copied as-is. \end{cfuncdesc} % --- MBCS codecs for Windows -------------------------------------------- These are the MBCS codec APIs. They are currently only available on Windows and use the Win32 MBCS converters to implement the conversions. Note that MBCS (or DBCS) is a class of encodings, not just one. The target encoding is defined by the user settings on the machine running the codec. \begin{cfuncdesc}{PyObject*}{PyUnicode_DecodeMBCS}{const char *s, int size, const char *errors} Creates a Unicode object by decoding \var{size} bytes of the MBCS encoded string \var{s}. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_EncodeMBCS}{const Py_UNICODE *s, int size, const char *errors} Encodes the \ctype{Py_UNICODE} buffer of the given size using MBCS and returns a Python string object. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_AsMBCSString}{PyObject *unicode} Encodes a Unicode objects using MBCS and returns the result as Python string object. Error handling is ``strict''. Returns \NULL{} if an exception was raised by the codec. \end{cfuncdesc} % --- Methods & Slots ---------------------------------------------------- \subsubsection{Methods and Slot Functions \label{unicodeMethodsAndSlots}} The following APIs are capable of handling Unicode objects and strings on input (we refer to them as strings in the descriptions) and return Unicode objects or integers as apporpriate. They all return \NULL{} or \code{-1} if an exception occurs. \begin{cfuncdesc}{PyObject*}{PyUnicode_Concat}{PyObject *left, PyObject *right} Concat two strings giving a new Unicode string. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Split}{PyObject *s, PyObject *sep, int maxsplit} Split a string giving a list of Unicode strings. If sep is \NULL, splitting will be done at all whitespace substrings. Otherwise, splits occur at the given separator. At most \var{maxsplit} splits will be done. If negative, no limit is set. Separators are not included in the resulting list. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Splitlines}{PyObject *s, int maxsplit} Split a Unicode string at line breaks, returning a list of Unicode strings. CRLF is considered to be one line break. The Line break characters are not included in the resulting strings. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Translate}{PyObject *str, PyObject *table, const char *errors} Translate a string by applying a character mapping table to it and return the resulting Unicode object. The mapping table must map Unicode ordinal integers to Unicode ordinal integers or None (causing deletion of the character). Mapping tables need only provide the \method{__getitem__()} interface; dictionaries and sequences work well. Unmapped character ordinals (ones which cause a \exception{LookupError}) are left untouched and are copied as-is. \var{errors} has the usual meaning for codecs. It may be \NULL{} which indicates to use the default error handling. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Join}{PyObject *separator, PyObject *seq} Join a sequence of strings using the given separator and return the resulting Unicode string. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Tailmatch}{PyObject *str, PyObject *substr, int start, int end, int direction} Return 1 if \var{substr} matches \var{str}[\var{start}:\var{end}] at the given tail end (\var{direction} == -1 means to do a prefix match, \var{direction} == 1 a suffix match), 0 otherwise. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_Find}{PyObject *str, PyObject *substr, int start, int end, int direction} Return the first position of \var{substr} in \var{str}[\var{start}:\var{end}] using the given \var{direction} (\var{direction} == 1 means to do a forward search, \var{direction} == -1 a backward search). The return value is the index of the first match; a value of \code{-1} indicates that no match was found, and \code{-2} indicates that an error occurred and an exception has been set. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_Count}{PyObject *str, PyObject *substr, int start, int end} Return the number of non-overlapping occurrences of \var{substr} in \code{\var{str}[\var{start}:\var{end}]}. Returns \code{-1} if an error occurred. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Replace}{PyObject *str, PyObject *substr, PyObject *replstr, int maxcount} Replace at most \var{maxcount} occurrences of \var{substr} in \var{str} with \var{replstr} and return the resulting Unicode object. \var{maxcount} == -1 means replace all occurrences. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_Compare}{PyObject *left, PyObject *right} Compare two strings and return -1, 0, 1 for less than, equal, and greater than, respectively. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyUnicode_Format}{PyObject *format, PyObject *args} Returns a new string object from \var{format} and \var{args}; this is analogous to \code{\var{format} \%\ \var{args}}. The \var{args} argument must be a tuple. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyUnicode_Contains}{PyObject *container, PyObject *element} Checks whether \var{element} is contained in \var{container} and returns true or false accordingly. \var{element} has to coerce to a one element Unicode string. \code{-1} is returned if there was an error. \end{cfuncdesc} \subsection{Buffer Objects \label{bufferObjects}} \sectionauthor{Greg Stein}{gstein@lyra.org} \obindex{buffer} Python objects implemented in C can export a group of functions called the ``buffer\index{buffer interface} interface.'' These functions can be used by an object to expose its data in a raw, byte-oriented format. Clients of the object can use the buffer interface to access the object data directly, without needing to copy it first. Two examples of objects that support the buffer interface are strings and arrays. The string object exposes the character contents in the buffer interface's byte-oriented form. An array can also expose its contents, but it should be noted that array elements may be multi-byte values. An example user of the buffer interface is the file object's \method{write()} method. Any object that can export a series of bytes through the buffer interface can be written to a file. There are a number of format codes to \cfunction{PyArg_ParseTuple()} that operate against an object's buffer interface, returning data from the target object. More information on the buffer interface is provided in the section ``Buffer Object Structures'' (section~\ref{buffer-structs}), under the description for \ctype{PyBufferProcs}\ttindex{PyBufferProcs}. A ``buffer object'' is defined in the \file{bufferobject.h} header (included by \file{Python.h}). These objects look very similar to string objects at the Python programming level: they support slicing, indexing, concatenation, and some other standard string operations. However, their data can come from one of two sources: from a block of memory, or from another object which exports the buffer interface. Buffer objects are useful as a way to expose the data from another object's buffer interface to the Python programmer. They can also be used as a zero-copy slicing mechanism. Using their ability to reference a block of memory, it is possible to expose any data to the Python programmer quite easily. The memory could be a large, constant array in a C extension, it could be a raw block of memory for manipulation before passing to an operating system library, or it could be used to pass around structured data in its native, in-memory format. \begin{ctypedesc}{PyBufferObject} This subtype of \ctype{PyObject} represents a buffer object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyBuffer_Type} The instance of \ctype{PyTypeObject} which represents the Python buffer type; it is the same object as \code{types.BufferType} in the Python layer.\withsubitem{(in module types)}{\ttindex{BufferType}}. \end{cvardesc} \begin{cvardesc}{int}{Py_END_OF_BUFFER} This constant may be passed as the \var{size} parameter to \cfunction{PyBuffer_FromObject()} or \cfunction{PyBuffer_FromReadWriteObject()}. It indicates that the new \ctype{PyBufferObject} should refer to \var{base} object from the specified \var{offset} to the end of its exported buffer. Using this enables the caller to avoid querying the \var{base} object for its length. \end{cvardesc} \begin{cfuncdesc}{int}{PyBuffer_Check}{PyObject *p} Return true if the argument has type \cdata{PyBuffer_Type}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyBuffer_FromObject}{PyObject *base, int offset, int size} Return a new read-only buffer object. This raises \exception{TypeError} if \var{base} doesn't support the read-only buffer protocol or doesn't provide exactly one buffer segment, or it raises \exception{ValueError} if \var{offset} is less than zero. The buffer will hold a reference to the \var{base} object, and the buffer's contents will refer to the \var{base} object's buffer interface, starting as position \var{offset} and extending for \var{size} bytes. If \var{size} is \constant{Py_END_OF_BUFFER}, then the new buffer's contents extend to the length of the \var{base} object's exported buffer data. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyBuffer_FromReadWriteObject}{PyObject *base, int offset, int size} Return a new writable buffer object. Parameters and exceptions are similar to those for \cfunction{PyBuffer_FromObject()}. If the \var{base} object does not export the writeable buffer protocol, then \exception{TypeError} is raised. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyBuffer_FromMemory}{void *ptr, int size} Return a new read-only buffer object that reads from a specified location in memory, with a specified size. The caller is responsible for ensuring that the memory buffer, passed in as \var{ptr}, is not deallocated while the returned buffer object exists. Raises \exception{ValueError} if \var{size} is less than zero. Note that \constant{Py_END_OF_BUFFER} may \emph{not} be passed for the \var{size} parameter; \exception{ValueError} will be raised in that case. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyBuffer_FromReadWriteMemory}{void *ptr, int size} Similar to \cfunction{PyBuffer_FromMemory()}, but the returned buffer is writable. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyBuffer_New}{int size} Returns a new writable buffer object that maintains its own memory buffer of \var{size} bytes. \exception{ValueError} is returned if \var{size} is not zero or positive. \end{cfuncdesc} \subsection{Tuple Objects \label{tupleObjects}} \obindex{tuple} \begin{ctypedesc}{PyTupleObject} This subtype of \ctype{PyObject} represents a Python tuple object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyTuple_Type} This instance of \ctype{PyTypeObject} represents the Python tuple type; it is the same object as \code{types.TupleType} in the Python layer.\withsubitem{(in module types)}{\ttindex{TupleType}}. \end{cvardesc} \begin{cfuncdesc}{int}{PyTuple_Check}{PyObject *p} Return true if \var{p} is a tuple object or an instance of a subtype of the tuple type. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyTuple_CheckExact}{PyObject *p} Return true if \var{p} is a tuple object, but not an instance of a subtype of the tuple type. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyTuple_New}{int len} Return a new tuple object of size \var{len}, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyTuple_Size}{PyObject *p} Takes a pointer to a tuple object, and returns the size of that tuple. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyTuple_GET_SIZE}{PyObject *p} Return the size of the tuple \var{p}, which must be non-\NULL{} and point to a tuple; no error checking is performed. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyTuple_GetItem}{PyObject *p, int pos} Returns the object at position \var{pos} in the tuple pointed to by \var{p}. If \var{pos} is out of bounds, returns \NULL{} and sets an \exception{IndexError} exception. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyTuple_GET_ITEM}{PyObject *p, int pos} Like \cfunction{PyTuple_GetItem()}, but does no checking of its arguments. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyTuple_GetSlice}{PyObject *p, int low, int high} Takes a slice of the tuple pointed to by \var{p} from \var{low} to \var{high} and returns it as a new tuple. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyTuple_SetItem}{PyObject *p, int pos, PyObject *o} Inserts a reference to object \var{o} at position \var{pos} of the tuple pointed to by \var{p}. It returns \code{0} on success. \note{This function ``steals'' a reference to \var{o}.} \end{cfuncdesc} \begin{cfuncdesc}{void}{PyTuple_SET_ITEM}{PyObject *p, int pos, PyObject *o} Like \cfunction{PyTuple_SetItem()}, but does no error checking, and should \emph{only} be used to fill in brand new tuples. \note{This function ``steals'' a reference to \var{o}.} \end{cfuncdesc} \begin{cfuncdesc}{int}{_PyTuple_Resize}{PyObject **p, int newsize} Can be used to resize a tuple. \var{newsize} will be the new length of the tuple. Because tuples are \emph{supposed} to be immutable, this should only be used if there is only one reference to the object. Do \emph{not} use this if the tuple may already be known to some other part of the code. The tuple will always grow or shrink at the end. Think of this as destroying the old tuple and creating a new one, only more efficiently. Returns \code{0} on success. Client code should never assume that the resulting value of \code{*\var{p}} will be the same as before calling this function. If the object referenced by \code{*\var{p}} is replaced, the original \code{*\var{p}} is destroyed. On failure, returns \code{-1} and sets \code{*\var{p}} to \NULL, and raises \exception{MemoryError} or \exception{SystemError}. \versionchanged[Removed unused third parameter, \var{last_is_sticky}]{2.2} \end{cfuncdesc} \subsection{List Objects \label{listObjects}} \obindex{list} \begin{ctypedesc}{PyListObject} This subtype of \ctype{PyObject} represents a Python list object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyList_Type} This instance of \ctype{PyTypeObject} represents the Python list type. This is the same object as \code{types.ListType}. \withsubitem{(in module types)}{\ttindex{ListType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyList_Check}{PyObject *p} Returns true if its argument is a \ctype{PyListObject}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyList_New}{int len} Returns a new list of length \var{len} on success, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_Size}{PyObject *list} Returns the length of the list object in \var{list}; this is equivalent to \samp{len(\var{list})} on a list object. \bifuncindex{len} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_GET_SIZE}{PyObject *list} Macro form of \cfunction{PyList_Size()} without error checking. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyList_GetItem}{PyObject *list, int index} Returns the object at position \var{pos} in the list pointed to by \var{p}. If \var{pos} is out of bounds, returns \NULL{} and sets an \exception{IndexError} exception. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyList_GET_ITEM}{PyObject *list, int i} Macro form of \cfunction{PyList_GetItem()} without error checking. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_SetItem}{PyObject *list, int index, PyObject *item} Sets the item at index \var{index} in list to \var{item}. Returns \code{0} on success or \code{-1} on failure. \note{This function ``steals'' a reference to \var{item} and discards a reference to an item already in the list at the affected position.} \end{cfuncdesc} \begin{cfuncdesc}{void}{PyList_SET_ITEM}{PyObject *list, int i, PyObject *o} Macro form of \cfunction{PyList_SetItem()} without error checking. This is normally only used to fill in new lists where there is no previous content. \note{This function ``steals'' a reference to \var{item}, and, unlike \cfunction{PyList_SetItem()}, does \emph{not} discard a reference to any item that it being replaced; any reference in \var{list} at position \var{i} will be leaked.} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_Insert}{PyObject *list, int index, PyObject *item} Inserts the item \var{item} into list \var{list} in front of index \var{index}. Returns \code{0} if successful; returns \code{-1} and raises an exception if unsuccessful. Analogous to \code{\var{list}.insert(\var{index}, \var{item})}. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_Append}{PyObject *list, PyObject *item} Appends the object \var{item} at the end of list \var{list}. Returns \code{0} if successful; returns \code{-1} and sets an exception if unsuccessful. Analogous to \code{\var{list}.append(\var{item})}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyList_GetSlice}{PyObject *list, int low, int high} Returns a list of the objects in \var{list} containing the objects \emph{between} \var{low} and \var{high}. Returns \NULL{} and sets an exception if unsuccessful. Analogous to \code{\var{list}[\var{low}:\var{high}]}. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_SetSlice}{PyObject *list, int low, int high, PyObject *itemlist} Sets the slice of \var{list} between \var{low} and \var{high} to the contents of \var{itemlist}. Analogous to \code{\var{list}[\var{low}:\var{high}] = \var{itemlist}}. Returns \code{0} on success, \code{-1} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_Sort}{PyObject *list} Sorts the items of \var{list} in place. Returns \code{0} on success, \code{-1} on failure. This is equivalent to \samp{\var{list}.sort()}. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyList_Reverse}{PyObject *list} Reverses the items of \var{list} in place. Returns \code{0} on success, \code{-1} on failure. This is the equivalent of \samp{\var{list}.reverse()}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyList_AsTuple}{PyObject *list} Returns a new tuple object containing the contents of \var{list}; equivalent to \samp{tuple(\var{list})}.\bifuncindex{tuple} \end{cfuncdesc} \section{Mapping Objects \label{mapObjects}} \obindex{mapping} \subsection{Dictionary Objects \label{dictObjects}} \obindex{dictionary} \begin{ctypedesc}{PyDictObject} This subtype of \ctype{PyObject} represents a Python dictionary object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyDict_Type} This instance of \ctype{PyTypeObject} represents the Python dictionary type. This is exposed to Python programs as \code{types.DictType} and \code{types.DictionaryType}. \withsubitem{(in module types)}{\ttindex{DictType}\ttindex{DictionaryType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyDict_Check}{PyObject *p} Returns true if its argument is a \ctype{PyDictObject}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_New}{} Returns a new empty dictionary, or \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDictProxy_New}{PyObject *dict} Return a proxy object for a mapping which enforces read-only behavior. This is normally used to create a proxy to prevent modification of the dictionary for non-dynamic class types. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{void}{PyDict_Clear}{PyObject *p} Empties an existing dictionary of all key-value pairs. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_Copy}{PyObject *p} Returns a new dictionary that contains the same key-value pairs as \var{p}. \versionadded{1.6} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_SetItem}{PyObject *p, PyObject *key, PyObject *val} Inserts \var{value} into the dictionary \var{p} with a key of \var{key}. \var{key} must be hashable; if it isn't, \exception{TypeError} will be raised. Returns \code{0} on success or \code{-1} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_SetItemString}{PyObject *p, char *key, PyObject *val} Inserts \var{value} into the dictionary \var{p} using \var{key} as a key. \var{key} should be a \ctype{char*}. The key object is created using \code{PyString_FromString(\var{key})}. Returns \code{0} on success or \code{-1} on failure. \ttindex{PyString_FromString()} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_DelItem}{PyObject *p, PyObject *key} Removes the entry in dictionary \var{p} with key \var{key}. \var{key} must be hashable; if it isn't, \exception{TypeError} is raised. Returns \code{0} on success or \code{-1} on failure. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_DelItemString}{PyObject *p, char *key} Removes the entry in dictionary \var{p} which has a key specified by the string \var{key}. Returns \code{0} on success or \code{-1} on failure. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_GetItem}{PyObject *p, PyObject *key} Returns the object from dictionary \var{p} which has a key \var{key}. Returns \NULL{} if the key \var{key} is not present, but \emph{without} setting an exception. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_GetItemString}{PyObject *p, char *key} This is the same as \cfunction{PyDict_GetItem()}, but \var{key} is specified as a \ctype{char*}, rather than a \ctype{PyObject*}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_Items}{PyObject *p} Returns a \ctype{PyListObject} containing all the items from the dictionary, as in the dictinoary method \method{items()} (see the \citetitle[../lib/lib.html]{Python Library Reference}). \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_Keys}{PyObject *p} Returns a \ctype{PyListObject} containing all the keys from the dictionary, as in the dictionary method \method{keys()} (see the \citetitle[../lib/lib.html]{Python Library Reference}). \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDict_Values}{PyObject *p} Returns a \ctype{PyListObject} containing all the values from the dictionary \var{p}, as in the dictionary method \method{values()} (see the \citetitle[../lib/lib.html]{Python Library Reference}). \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_Size}{PyObject *p} Returns the number of items in the dictionary. This is equivalent to \samp{len(\var{p})} on a dictionary.\bifuncindex{len} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_Next}{PyObject *p, int *ppos, PyObject **pkey, PyObject **pvalue} Iterate over all key-value pairs in the dictionary \var{p}. The \ctype{int} referred to by \var{ppos} must be initialized to \code{0} prior to the first call to this function to start the iteration; the function returns true for each pair in the dictionary, and false once all pairs have been reported. The parameters \var{pkey} and \var{pvalue} should either point to \ctype{PyObject*} variables that will be filled in with each key and value, respectively, or may be \NULL. Any references returned through them are borrowed. For example: \begin{verbatim} PyObject *key, *value; int pos = 0; while (PyDict_Next(self->dict, &pos, &key, &value)) { /* do something interesting with the values... */ ... } \end{verbatim} The dictionary \var{p} should not be mutated during iteration. It is safe (since Python 2.1) to modify the values of the keys as you iterate over the dictionary, but only so long as the set of keys does not change. For example: \begin{verbatim} PyObject *key, *value; int pos = 0; while (PyDict_Next(self->dict, &pos, &key, &value)) { int i = PyInt_AS_LONG(value) + 1; PyObject *o = PyInt_FromLong(i); if (o == NULL) return -1; if (PyDict_SetItem(self->dict, key, o) < 0) { Py_DECREF(o); return -1; } Py_DECREF(o); } \end{verbatim} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_Merge}{PyObject *a, PyObject *b, int override} Iterate over mapping object \var{b} adding key-value pairs to dictionary \var{a}. \var{b} may be a dictionary, or any object supporting \function{PyMapping_Keys()} and \function{PyObject_GetItem()}. If \var{override} is true, existing pairs in \var{a} will be replaced if a matching key is found in \var{b}, otherwise pairs will only be added if there is not a matching key in \var{a}. Return \code{0} on success or \code{-1} if an exception was raised. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_Update}{PyObject *a, PyObject *b} This is the same as \code{PyDict_Merge(\var{a}, \var{b}, 1)} in C, or \code{\var{a}.update(\var{b})} in Python. Return \code{0} on success or \code{-1} if an exception was raised. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDict_MergeFromSeq2}{PyObject *a, PyObject *seq2, int override} Update or merge into dictionary \var{a}, from the key-value pairs in \var{seq2}. \var{seq2} must be an iterable object producing iterable objects of length 2, viewed as key-value pairs. In case of duplicate keys, the last wins if \var{override} is true, else the first wins. Return \code{0} on success or \code{-1} if an exception was raised. Equivalent Python (except for the return value): \begin{verbatim} def PyDict_MergeFromSeq2(a, seq2, override): for key, value in seq2: if override or key not in a: a[key] = value \end{verbatim} \versionadded{2.2} \end{cfuncdesc} \section{Other Objects \label{otherObjects}} \subsection{File Objects \label{fileObjects}} \obindex{file} Python's built-in file objects are implemented entirely on the \ctype{FILE*} support from the C standard library. This is an implementation detail and may change in future releases of Python. \begin{ctypedesc}{PyFileObject} This subtype of \ctype{PyObject} represents a Python file object. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyFile_Type} This instance of \ctype{PyTypeObject} represents the Python file type. This is exposed to Python programs as \code{types.FileType}. \withsubitem{(in module types)}{\ttindex{FileType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyFile_Check}{PyObject *p} Returns true if its argument is a \ctype{PyFileObject} or a subtype of \ctype{PyFileObject}. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyFile_CheckExact}{PyObject *p} Returns true if its argument is a \ctype{PyFileObject}, but not a subtype of \ctype{PyFileObject}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFile_FromString}{char *filename, char *mode} On success, returns a new file object that is opened on the file given by \var{filename}, with a file mode given by \var{mode}, where \var{mode} has the same semantics as the standard C routine \cfunction{fopen()}\ttindex{fopen()}. On failure, returns \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFile_FromFile}{FILE *fp, char *name, char *mode, int (*close)(FILE*)} Creates a new \ctype{PyFileObject} from the already-open standard C file pointer, \var{fp}. The function \var{close} will be called when the file should be closed. Returns \NULL{} on failure. \end{cfuncdesc} \begin{cfuncdesc}{FILE*}{PyFile_AsFile}{PyFileObject *p} Returns the file object associated with \var{p} as a \ctype{FILE*}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFile_GetLine}{PyObject *p, int n} Equivalent to \code{\var{p}.readline(\optional{\var{n}})}, this function reads one line from the object \var{p}. \var{p} may be a file object or any object with a \method{readline()} method. If \var{n} is \code{0}, exactly one line is read, regardless of the length of the line. If \var{n} is greater than \code{0}, no more than \var{n} bytes will be read from the file; a partial line can be returned. In both cases, an empty string is returned if the end of the file is reached immediately. If \var{n} is less than \code{0}, however, one line is read regardless of length, but \exception{EOFError} is raised if the end of the file is reached immediately. \withsubitem{(built-in exception)}{\ttindex{EOFError}} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyFile_Name}{PyObject *p} Returns the name of the file specified by \var{p} as a string object. \end{cfuncdesc} \begin{cfuncdesc}{void}{PyFile_SetBufSize}{PyFileObject *p, int n} Available on systems with \cfunction{setvbuf()}\ttindex{setvbuf()} only. This should only be called immediately after file object creation. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyFile_SoftSpace}{PyObject *p, int newflag} This function exists for internal use by the interpreter. Sets the \member{softspace} attribute of \var{p} to \var{newflag} and \withsubitem{(file attribute)}{\ttindex{softspace}}returns the previous value. \var{p} does not have to be a file object for this function to work properly; any object is supported (thought its only interesting if the \member{softspace} attribute can be set). This function clears any errors, and will return \code{0} as the previous value if the attribute either does not exist or if there were errors in retrieving it. There is no way to detect errors from this function, but doing so should not be needed. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyFile_WriteObject}{PyObject *obj, PyFileObject *p, int flags} Writes object \var{obj} to file object \var{p}. The only supported flag for \var{flags} is \constant{Py_PRINT_RAW}\ttindex{Py_PRINT_RAW}; if given, the \function{str()} of the object is written instead of the \function{repr()}. Returns \code{0} on success or \code{-1} on failure; the appropriate exception will be set. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyFile_WriteString}{const char *s, PyFileObject *p} Writes string \var{s} to file object \var{p}. Returns \code{0} on success or \code{-1} on failure; the appropriate exception will be set. \end{cfuncdesc} \subsection{Instance Objects \label{instanceObjects}} \obindex{instance} There are very few functions specific to instance objects. \begin{cvardesc}{PyTypeObject}{PyInstance_Type} Type object for class instances. \end{cvardesc} \begin{cfuncdesc}{int}{PyInstance_Check}{PyObject *obj} Returns true if \var{obj} is an instance. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyInstance_New}{PyObject *class, PyObject *arg, PyObject *kw} Create a new instance of a specific class. The parameters \var{arg} and \var{kw} are used as the positional and keyword parameters to the object's constructor. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyInstance_NewRaw}{PyObject *class, PyObject *dict} Create a new instance of a specific class without calling it's constructor. \var{class} is the class of new object. The \var{dict} parameter will be used as the object's \member{__dict__}; if \NULL, a new dictionary will be created for the instance. \end{cfuncdesc} \subsection{Method Objects \label{method-objects}} \obindex{method} There are some useful functions that are useful for working with method objects. \begin{cvardesc}{PyTypeObject}{PyMethod_Type} This instance of \ctype{PyTypeObject} represents the Python method type. This is exposed to Python programs as \code{types.MethodType}. \withsubitem{(in module types)}{\ttindex{MethodType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyMethod_Check}{PyObject *o} Return true if \var{o} is a method object (has type \cdata{PyMethod_Type}). The parameter must not be \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_New}{PyObject *func. PyObject *self, PyObject *class} Return a new method object, with \var{func} being any callable object; this is the function that will be called when the method is called. If this method should be bound to an instance, \var{self} should be the instance and \var{class} should be the class of \var{self}, otherwise \var{self} should be \NULL{} and \var{class} should be the class which provides the unbound method.. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_Class}{PyObject *meth} Return the class object from which the method \var{meth} was created; if this was created from an instance, it will be the class of the instance. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_GET_CLASS}{PyObject *meth} Macro version of \cfunction{PyMethod_Class()} which avoids error checking. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_Function}{PyObject *meth} Return the function object associated with the method \var{meth}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_GET_FUNCTION}{PyObject *meth} Macro version of \cfunction{PyMethod_Function()} which avoids error checking. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_Self}{PyObject *meth} Return the instance associated with the method \var{meth} if it is bound, otherwise return \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyMethod_GET_SELF}{PyObject *meth} Macro version of \cfunction{PyMethod_Self()} which avoids error checking. \end{cfuncdesc} \subsection{Module Objects \label{moduleObjects}} \obindex{module} There are only a few functions special to module objects. \begin{cvardesc}{PyTypeObject}{PyModule_Type} This instance of \ctype{PyTypeObject} represents the Python module type. This is exposed to Python programs as \code{types.ModuleType}. \withsubitem{(in module types)}{\ttindex{ModuleType}} \end{cvardesc} \begin{cfuncdesc}{int}{PyModule_Check}{PyObject *p} Returns true if \var{p} is a module object, or a subtype of a module object. \versionchanged[Allowed subtypes to be accepted]{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyModule_CheckExact}{PyObject *p} Returns true if \var{p} is a module object, but not a subtype of \cdata{PyModule_Type}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyModule_New}{char *name} Return a new module object with the \member{__name__} attribute set to \var{name}. Only the module's \member{__doc__} and \member{__name__} attributes are filled in; the caller is responsible for providing a \member{__file__} attribute. \withsubitem{(module attribute)}{ \ttindex{__name__}\ttindex{__doc__}\ttindex{__file__}} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyModule_GetDict}{PyObject *module} Return the dictionary object that implements \var{module}'s namespace; this object is the same as the \member{__dict__} attribute of the module object. This function never fails. \withsubitem{(module attribute)}{\ttindex{__dict__}} It is recommended extensions use other \cfunction{PyModule_*()} and \cfunction{PyObject_*()} functions rather than directly manipulate a module's \member{__dict__}. \end{cfuncdesc} \begin{cfuncdesc}{char*}{PyModule_GetName}{PyObject *module} Return \var{module}'s \member{__name__} value. If the module does not provide one, or if it is not a string, \exception{SystemError} is raised and \NULL{} is returned. \withsubitem{(module attribute)}{\ttindex{__name__}} \withsubitem{(built-in exception)}{\ttindex{SystemError}} \end{cfuncdesc} \begin{cfuncdesc}{char*}{PyModule_GetFilename}{PyObject *module} Return the name of the file from which \var{module} was loaded using \var{module}'s \member{__file__} attribute. If this is not defined, or if it is not a string, raise \exception{SystemError} and return \NULL. \withsubitem{(module attribute)}{\ttindex{__file__}} \withsubitem{(built-in exception)}{\ttindex{SystemError}} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyModule_AddObject}{PyObject *module, char *name, PyObject *value} Add an object to \var{module} as \var{name}. This is a convenience function which can be used from the module's initialization function. This steals a reference to \var{value}. Returns \code{-1} on error, \code{0} on success. \versionadded{2.0} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyModule_AddIntConstant}{PyObject *module, char *name, int value} Add an integer constant to \var{module} as \var{name}. This convenience function can be used from the module's initialization function. Returns \code{-1} on error, \code{0} on success. \versionadded{2.0} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyModule_AddStringConstant}{PyObject *module, char *name, char *value} Add a string constant to \var{module} as \var{name}. This convenience function can be used from the module's initialization function. The string \var{value} must be null-terminated. Returns \code{-1} on error, \code{0} on success. \versionadded{2.0} \end{cfuncdesc} \subsection{Iterator Objects \label{iterator-objects}} Python provides two general-purpose iterator objects. The first, a sequence iterator, works with an arbitrary sequence supporting the \method{__getitem__()} method. The second works with a callable object and a sentinel value, calling the callable for each item in the sequence, and ending the iteration when the sentinel value is returned. \begin{cvardesc}{PyTypeObject}{PySeqIter_Type} Type object for iterator objects returned by \cfunction{PySeqIter_New()} and the one-argument form of the \function{iter()} built-in function for built-in sequence types. \versionadded{2.2} \end{cvardesc} \begin{cfuncdesc}{int}{PySeqIter_Check}{op} Return true if the type of \var{op} is \cdata{PySeqIter_Type}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PySeqIter_New}{PyObject *seq} Return an iterator that works with a general sequence object, \var{seq}. The iteration ends when the sequence raises \exception{IndexError} for the subscripting operation. \versionadded{2.2} \end{cfuncdesc} \begin{cvardesc}{PyTypeObject}{PyCallIter_Type} Type object for iterator objects returned by \cfunction{PyCallIter_New()} and the two-argument form of the \function{iter()} built-in function. \versionadded{2.2} \end{cvardesc} \begin{cfuncdesc}{int}{PyCallIter_Check}{op} Return true if the type of \var{op} is \cdata{PyCallIter_Type}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCallIter_New}{PyObject *callable, PyObject *sentinel} Return a new iterator. The first parameter, \var{callable}, can be any Python callable object that can be called with no parameters; each call to it should return the next item in the iteration. When \var{callable} returns a value equal to \var{sentinel}, the iteration will be terminated. \versionadded{2.2} \end{cfuncdesc} \subsection{Descriptor Objects \label{descriptor-objects}} ``Descriptors'' are objects that describe some attribute of an object. They are found in the dictionary of type objects. \begin{cvardesc}{PyTypeObject}{PyProperty_Type} The type object for the built-in descriptor types. \versionadded{2.2} \end{cvardesc} \begin{cfuncdesc}{PyObject*}{PyDescr_NewGetSet}{PyTypeObject *type, PyGetSetDef *getset} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDescr_NewMember}{PyTypeObject *type, PyMemberDef *meth} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDescr_NewMethod}{PyTypeObject *type, PyMethodDef *meth} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyDescr_NewWrapper}{PyTypeObject *type, struct wrapperbase *wrapper, void *wrapped} \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyDescr_IsData}{PyObject *descr} Returns true if the descriptor objects \var{descr} describes a data attribute, or false if it describes a method. \var{descr} must be a descriptor object; there is no error checking. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyWrapper_New}{PyObject *, PyObject *} \versionadded{2.2} \end{cfuncdesc} \subsection{Slice Objects \label{slice-objects}} \begin{cvardesc}{PyTypeObject}{PySlice_Type} The type object for slice objects. This is the same as \code{types.SliceType}. \withsubitem{(in module types)}{\ttindex{SliceType}} \end{cvardesc} \begin{cfuncdesc}{int}{PySlice_Check}{PyObject *ob} Returns true if \var{ob} is a slice object; \var{ob} must not be \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PySlice_New}{PyObject *start, PyObject *stop, PyObject *step} Return a new slice object with the given values. The \var{start}, \var{stop}, and \var{step} parameters are used as the values of the slice object attributes of the same names. Any of the values may be \NULL, in which case the \code{None} will be used for the corresponding attribute. Returns \NULL{} if the new object could not be allocated. \end{cfuncdesc} \begin{cfuncdesc}{int}{PySlice_GetIndices}{PySliceObject *slice, int length, int *start, int *stop, int *step} Retrieve the start, stop and step indices from the slice object \var{slice}, assuming a sequence of length \var{length}. Treats indices greater than \var{length} as errors. Returns 0 on success and -1 on error with no exception set (unless one of the indices was not \constant{None} and failed to be converted to an integer, in which case -1 is returned with an exception set). You probably do not want to use this function. If you want to use slice objects in versions of Python prior to 2.3, you would probably do well to incorporate the source of \cfunction{PySlice_GetIndicesEx}, suitably renamed, in the source of your extension. \end{cfuncdesc} \begin{cfuncdesc}{int}{PySlice_GetIndicesEx}{PySliceObject *slice, int length, int *start, int *stop, int *step, int *slicelength} Usable replacement for \cfunction{PySlice_GetIndices}. Retrieve the start, stop, and step indices from the slice object \var{slice} assuming a sequence of length \var{length}, and store the length of the slice in \var{slicelength}. Out of bounds indices are clipped in a manner consistent with the handling of normal slices. Returns 0 on success and -1 on error with exception set. \versionadded{2.3} \end{cfuncdesc} \subsection{Weak Reference Objects \label{weakref-objects}} Python supports \emph{weak references} as first-class objects. There are two specific object types which directly implement weak references. The first is a simple reference object, and the second acts as a proxy for the original object as much as it can. \begin{cfuncdesc}{int}{PyWeakref_Check}{ob} Return true if \var{ob} is either a reference or proxy object. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyWeakref_CheckRef}{ob} Return true if \var{ob} is a reference object. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{int}{PyWeakref_CheckProxy}{ob} Return true if \var{ob} is a proxy object. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyWeakref_NewRef}{PyObject *ob, PyObject *callback} Return a weak reference object for the object \var{ob}. This will always return a new reference, but is not guaranteed to create a new object; an existing reference object may be returned. The second parameter, \var{callback}, can be a callable object that receives notification when \var{ob} is garbage collected; it should accept a single paramter, which will be the weak reference object itself. \var{callback} may also be \code{None} or \NULL. If \var{ob} is not a weakly-referencable object, or if \var{callback} is not callable, \code{None}, or \NULL, this will return \NULL{} and raise \exception{TypeError}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyWeakref_NewProxy}{PyObject *ob, PyObject *callback} Return a weak reference proxy object for the object \var{ob}. This will always return a new reference, but is not guaranteed to create a new object; an existing proxy object may be returned. The second parameter, \var{callback}, can be a callable object that receives notification when \var{ob} is garbage collected; it should accept a single paramter, which will be the weak reference object itself. \var{callback} may also be \code{None} or \NULL. If \var{ob} is not a weakly-referencable object, or if \var{callback} is not callable, \code{None}, or \NULL, this will return \NULL{} and raise \exception{TypeError}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyWeakref_GetObject}{PyObject *ref} Returns the referenced object from a weak reference, \var{ref}. If the referent is no longer live, returns \code{None}. \versionadded{2.2} \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyWeakref_GET_OBJECT}{PyObject *ref} Similar to \cfunction{PyWeakref_GetObject()}, but implemented as a macro that does no error checking. \versionadded{2.2} \end{cfuncdesc} \subsection{CObjects \label{cObjects}} \obindex{CObject} Refer to \emph{Extending and Embedding the Python Interpreter}, section~1.12, ``Providing a C API for an Extension Module,'' for more information on using these objects. \begin{ctypedesc}{PyCObject} This subtype of \ctype{PyObject} represents an opaque value, useful for C extension modules who need to pass an opaque value (as a \ctype{void*} pointer) through Python code to other C code. It is often used to make a C function pointer defined in one module available to other modules, so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules. \end{ctypedesc} \begin{cfuncdesc}{int}{PyCObject_Check}{PyObject *p} Returns true if its argument is a \ctype{PyCObject}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCObject_FromVoidPtr}{void* cobj, void (*destr)(void *)} Creates a \ctype{PyCObject} from the \code{void *}\var{cobj}. The \var{destr} function will be called when the object is reclaimed, unless it is \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCObject_FromVoidPtrAndDesc}{void* cobj, void* desc, void (*destr)(void *, void *)} Creates a \ctype{PyCObject} from the \ctype{void *}\var{cobj}. The \var{destr} function will be called when the object is reclaimed. The \var{desc} argument can be used to pass extra callback data for the destructor function. \end{cfuncdesc} \begin{cfuncdesc}{void*}{PyCObject_AsVoidPtr}{PyObject* self} Returns the object \ctype{void *} that the \ctype{PyCObject} \var{self} was created with. \end{cfuncdesc} \begin{cfuncdesc}{void*}{PyCObject_GetDesc}{PyObject* self} Returns the description \ctype{void *} that the \ctype{PyCObject} \var{self} was created with. \end{cfuncdesc} \subsection{Cell Objects \label{cell-objects}} ``Cell'' objects are used to implement variables referenced by multiple scopes. For each such variable, a cell object is created to store the value; the local variables of each stack frame that references the value contains a reference to the cells from outer scopes which also use that variable. When the value is accessed, the value contained in the cell is used instead of the cell object itself. This de-referencing of the cell object requires support from the generated byte-code; these are not automatically de-referenced when accessed. Cell objects are not likely to be useful elsewhere. \begin{ctypedesc}{PyCellObject} The C structure used for cell objects. \end{ctypedesc} \begin{cvardesc}{PyTypeObject}{PyCell_Type} The type object corresponding to cell objects \end{cvardesc} \begin{cfuncdesc}{int}{PyCell_Check}{ob} Return true if \var{ob} is a cell object; \var{ob} must not be \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCell_New}{PyObject *ob} Create and return a new cell object containing the value \var{ob}. The parameter may be \NULL. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCell_Get}{PyObject *cell} Return the contents of the cell \var{cell}. \end{cfuncdesc} \begin{cfuncdesc}{PyObject*}{PyCell_GET}{PyObject *cell} Return the contents of the cell \var{cell}, but without checking that \var{cell} is non-\NULL{} and a call object. \end{cfuncdesc} \begin{cfuncdesc}{int}{PyCell_Set}{PyObject *cell, PyObject *value} Set the contents of the cell object \var{cell} to \var{value}. This releases the reference to any current content of the cell. \var{value} may be \NULL. \var{cell} must be non-\NULL; if it is not a cell object, \code{-1} will be returned. On success, \code{0} will be returned. \end{cfuncdesc} \begin{cfuncdesc}{void}{PyCell_SET}{PyObject *cell, PyObject *value} Sets the value of the cell object \var{cell} to \var{value}. No reference counts are adjusted, and no checks are made for safety; \var{cell} must be non-\NULL{} and must be a cell object. \end{cfuncdesc}