diff options
author | Jeroen Ruigrok van der Werven <asmodai@in-nomine.org> | 2009-04-25 13:58:58 (GMT) |
---|---|---|
committer | Jeroen Ruigrok van der Werven <asmodai@in-nomine.org> | 2009-04-25 13:58:58 (GMT) |
commit | 140d9d673efdb33178fb4f93ece31bbc1d91ada0 (patch) | |
tree | d06c26cf697d80654b73befee7c539bc0be0e526 | |
parent | 2dcf46ee2cddce17f18081ea7fa3535caad652dc (diff) | |
download | cpython-140d9d673efdb33178fb4f93ece31bbc1d91ada0.zip cpython-140d9d673efdb33178fb4f93ece31bbc1d91ada0.tar.gz cpython-140d9d673efdb33178fb4f93ece31bbc1d91ada0.tar.bz2 |
Reformat file prior to editing.
-rw-r--r-- | Doc/c-api/arg.rst | 491 |
1 files changed, 252 insertions, 239 deletions
diff --git a/Doc/c-api/arg.rst b/Doc/c-api/arg.rst index 9d14d1c..e7d997f 100644 --- a/Doc/c-api/arg.rst +++ b/Doc/c-api/arg.rst @@ -10,46 +10,48 @@ methods. Additional information and examples are available in :ref:`extending-index`. The first three of these functions described, :cfunc:`PyArg_ParseTuple`, -:cfunc:`PyArg_ParseTupleAndKeywords`, and :cfunc:`PyArg_Parse`, all use *format -strings* which are used to tell the function about the expected arguments. The -format strings use the same syntax for each of these functions. +:cfunc:`PyArg_ParseTupleAndKeywords`, and :cfunc:`PyArg_Parse`, all use +*format strings* which are used to tell the function about the expected +arguments. The format strings use the same syntax for each of these +functions. A format string consists of zero or more "format units." A format unit -describes one Python object; it is usually a single character or a parenthesized -sequence of format units. With a few exceptions, a format unit that is not a -parenthesized sequence normally corresponds to a single address argument to -these functions. In the following description, the quoted form is the format -unit; the entry in (round) parentheses is the Python object type that matches -the format unit; and the entry in [square] brackets is the type of the C -variable(s) whose address should be passed. +describes one Python object; it is usually a single character or a +parenthesized sequence of format units. With a few exceptions, a format unit +that is not a parenthesized sequence normally corresponds to a single address +argument to these functions. In the following description, the quoted form is +the format unit; the entry in (round) parentheses is the Python object type +that matches the format unit; and the entry in [square] brackets is the type +of the C variable(s) whose address should be passed. ``s`` (string or Unicode object) [const char \*] - Convert a Python string or Unicode object to a C pointer to a character string. - You must not provide storage for the string itself; a pointer to an existing - string is stored into the character pointer variable whose address you pass. - The C string is NUL-terminated. The Python string must not contain embedded NUL - bytes; if it does, a :exc:`TypeError` exception is raised. Unicode objects are - converted to C strings using the default encoding. If this conversion fails, a - :exc:`UnicodeError` is raised. + Convert a Python string or Unicode object to a C pointer to a character + string. You must not provide storage for the string itself; a pointer to + an existing string is stored into the character pointer variable whose + address you pass. The C string is NUL-terminated. The Python string must + not contain embedded NUL bytes; if it does, a :exc:`TypeError` exception is + raised. Unicode objects are converted to C strings using the default + encoding. If this conversion fails, a :exc:`UnicodeError` is raised. ``s#`` (string, Unicode or any read buffer compatible object) [const char \*, int (or :ctype:`Py_ssize_t`, see below)] - This variant on ``s`` stores into two C variables, the first one a pointer to a - character string, the second one its length. In this case the Python string may - contain embedded null bytes. Unicode objects pass back a pointer to the default - encoded string version of the object if such a conversion is possible. All - other read-buffer compatible objects pass back a reference to the raw internal - data representation. - - Starting with Python 2.5 the type of the length argument can be - controlled by defining the macro :cmacro:`PY_SSIZE_T_CLEAN` before - including :file:`Python.h`. If the macro is defined, length is a - :ctype:`Py_ssize_t` rather than an int. + This variant on ``s`` stores into two C variables, the first one a pointer + to a character string, the second one its length. In this case the Python + string may contain embedded null bytes. Unicode objects pass back a + pointer to the default encoded string version of the object if such a + conversion is possible. All other read-buffer compatible objects pass back + a reference to the raw internal data representation. + + Starting with Python 2.5 the type of the length argument can be controlled + by defining the macro :cmacro:`PY_SSIZE_T_CLEAN` before including + :file:`Python.h`. If the macro is defined, length is a :ctype:`Py_ssize_t` + rather than an int. ``s*`` (string, Unicode, or any buffer compatible object) [Py_buffer \*] - Similar to ``s#``, this code fills a Py_buffer structure provided by the caller. - The buffer gets locked, so that the caller can subsequently use the buffer even - inside a ``Py_BEGIN_ALLOW_THREADS`` block; the caller is responsible for calling - ``PyBuffer_Release`` with the structure after it has processed the data. + Similar to ``s#``, this code fills a Py_buffer structure provided by the + caller. The buffer gets locked, so that the caller can subsequently use + the buffer even inside a ``Py_BEGIN_ALLOW_THREADS`` block; the caller is + responsible for calling ``PyBuffer_Release`` with the structure after it + has processed the data. .. versionadded:: 2.6 @@ -66,83 +68,86 @@ variable(s) whose address should be passed. .. versionadded:: 2.6 ``u`` (Unicode object) [Py_UNICODE \*] - Convert a Python Unicode object to a C pointer to a NUL-terminated buffer of - 16-bit Unicode (UTF-16) data. As with ``s``, there is no need to provide - storage for the Unicode data buffer; a pointer to the existing Unicode data is - stored into the :ctype:`Py_UNICODE` pointer variable whose address you pass. + Convert a Python Unicode object to a C pointer to a NUL-terminated buffer + of 16-bit Unicode (UTF-16) data. As with ``s``, there is no need to + provide storage for the Unicode data buffer; a pointer to the existing + Unicode data is stored into the :ctype:`Py_UNICODE` pointer variable whose + address you pass. ``u#`` (Unicode object) [Py_UNICODE \*, int] - This variant on ``u`` stores into two C variables, the first one a pointer to a - Unicode data buffer, the second one its length. Non-Unicode objects are handled - by interpreting their read-buffer pointer as pointer to a :ctype:`Py_UNICODE` - array. + This variant on ``u`` stores into two C variables, the first one a pointer + to a Unicode data buffer, the second one its length. Non-Unicode objects + are handled by interpreting their read-buffer pointer as pointer to a + :ctype:`Py_UNICODE` array. ``es`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer] - This variant on ``s`` is used for encoding Unicode and objects convertible to - Unicode into a character buffer. It only works for encoded data without embedded - NUL bytes. + This variant on ``s`` is used for encoding Unicode and objects convertible + to Unicode into a character buffer. It only works for encoded data without + embedded NUL bytes. This format requires two arguments. The first is only used as input, and - must be a :ctype:`const char\*` which points to the name of an encoding as a - NUL-terminated string, or *NULL*, in which case the default encoding is used. - An exception is raised if the named encoding is not known to Python. The - second argument must be a :ctype:`char\*\*`; the value of the pointer it - references will be set to a buffer with the contents of the argument text. - The text will be encoded in the encoding specified by the first argument. - - :cfunc:`PyArg_ParseTuple` will allocate a buffer of the needed size, copy the - encoded data into this buffer and adjust *\*buffer* to reference the newly - allocated storage. The caller is responsible for calling :cfunc:`PyMem_Free` to - free the allocated buffer after use. + must be a :ctype:`const char\*` which points to the name of an encoding as + a NUL-terminated string, or *NULL*, in which case the default encoding is + used. An exception is raised if the named encoding is not known to Python. + The second argument must be a :ctype:`char\*\*`; the value of the pointer + it references will be set to a buffer with the contents of the argument + text. The text will be encoded in the encoding specified by the first + argument. + + :cfunc:`PyArg_ParseTuple` will allocate a buffer of the needed size, copy + the encoded data into this buffer and adjust *\*buffer* to reference the + newly allocated storage. The caller is responsible for calling + :cfunc:`PyMem_Free` to free the allocated buffer after use. ``et`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer] Same as ``es`` except that 8-bit string objects are passed through without - recoding them. Instead, the implementation assumes that the string object uses - the encoding passed in as parameter. + recoding them. Instead, the implementation assumes that the string object + uses the encoding passed in as parameter. ``es#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer, int \*buffer_length] - This variant on ``s#`` is used for encoding Unicode and objects convertible to - Unicode into a character buffer. Unlike the ``es`` format, this variant allows - input data which contains NUL characters. - - It requires three arguments. The first is only used as input, and must be a - :ctype:`const char\*` which points to the name of an encoding as a - NUL-terminated string, or *NULL*, in which case the default encoding is used. - An exception is raised if the named encoding is not known to Python. The - second argument must be a :ctype:`char\*\*`; the value of the pointer it - references will be set to a buffer with the contents of the argument text. - The text will be encoded in the encoding specified by the first argument. - The third argument must be a pointer to an integer; the referenced integer - will be set to the number of bytes in the output buffer. + This variant on ``s#`` is used for encoding Unicode and objects convertible + to Unicode into a character buffer. Unlike the ``es`` format, this variant + allows input data which contains NUL characters. + + It requires three arguments. The first is only used as input, and must be + a :ctype:`const char\*` which points to the name of an encoding as a + NUL-terminated string, or *NULL*, in which case the default encoding is + used. An exception is raised if the named encoding is not known to Python. + The second argument must be a :ctype:`char\*\*`; the value of the pointer + it references will be set to a buffer with the contents of the argument + text. The text will be encoded in the encoding specified by the first + argument. The third argument must be a pointer to an integer; the + referenced integer will be set to the number of bytes in the output buffer. There are two modes of operation: - If *\*buffer* points a *NULL* pointer, the function will allocate a buffer of - the needed size, copy the encoded data into this buffer and set *\*buffer* to - reference the newly allocated storage. The caller is responsible for calling - :cfunc:`PyMem_Free` to free the allocated buffer after usage. + If *\*buffer* points a *NULL* pointer, the function will allocate a buffer + of the needed size, copy the encoded data into this buffer and set + *\*buffer* to reference the newly allocated storage. The caller is + responsible for calling :cfunc:`PyMem_Free` to free the allocated buffer + after usage. If *\*buffer* points to a non-*NULL* pointer (an already allocated buffer), - :cfunc:`PyArg_ParseTuple` will use this location as the buffer and interpret the - initial value of *\*buffer_length* as the buffer size. It will then copy the - encoded data into the buffer and NUL-terminate it. If the buffer is not large - enough, a :exc:`ValueError` will be set. + :cfunc:`PyArg_ParseTuple` will use this location as the buffer and + interpret the initial value of *\*buffer_length* as the buffer size. It + will then copy the encoded data into the buffer and NUL-terminate it. If + the buffer is not large enough, a :exc:`ValueError` will be set. In both cases, *\*buffer_length* is set to the length of the encoded data without the trailing NUL byte. ``et#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer] - Same as ``es#`` except that string objects are passed through without recoding - them. Instead, the implementation assumes that the string object uses the - encoding passed in as parameter. + Same as ``es#`` except that string objects are passed through without + recoding them. Instead, the implementation assumes that the string object + uses the encoding passed in as parameter. ``b`` (integer) [unsigned char] Convert a nonnegative Python integer to an unsigned tiny int, stored in a C :ctype:`unsigned char`. ``B`` (integer) [unsigned char] - Convert a Python integer to a tiny int without overflow checking, stored in a C - :ctype:`unsigned char`. + Convert a Python integer to a tiny int without overflow checking, stored in + a C :ctype:`unsigned char`. .. versionadded:: 2.3 @@ -150,8 +155,8 @@ variable(s) whose address should be passed. Convert a Python integer to a C :ctype:`short int`. ``H`` (integer) [unsigned short int] - Convert a Python integer to a C :ctype:`unsigned short int`, without overflow - checking. + Convert a Python integer to a C :ctype:`unsigned short int`, without + overflow checking. .. versionadded:: 2.3 @@ -168,20 +173,21 @@ variable(s) whose address should be passed. Convert a Python integer to a C :ctype:`long int`. ``k`` (integer) [unsigned long] - Convert a Python integer or long integer to a C :ctype:`unsigned long` without - overflow checking. + Convert a Python integer or long integer to a C :ctype:`unsigned long` + without overflow checking. .. versionadded:: 2.3 ``L`` (integer) [PY_LONG_LONG] Convert a Python integer to a C :ctype:`long long`. This format is only - available on platforms that support :ctype:`long long` (or :ctype:`_int64` on - Windows). + available on platforms that support :ctype:`long long` (or :ctype:`_int64` + on Windows). ``K`` (integer) [unsigned PY_LONG_LONG] Convert a Python integer or long integer to a C :ctype:`unsigned long long` without overflow checking. This format is only available on platforms that - support :ctype:`unsigned long long` (or :ctype:`unsigned _int64` on Windows). + support :ctype:`unsigned long long` (or :ctype:`unsigned _int64` on + Windows). .. versionadded:: 2.3 @@ -204,60 +210,61 @@ variable(s) whose address should be passed. Convert a Python complex number to a C :ctype:`Py_complex` structure. ``O`` (object) [PyObject \*] - Store a Python object (without any conversion) in a C object pointer. The C - program thus receives the actual object that was passed. The object's reference - count is not increased. The pointer stored is not *NULL*. + Store a Python object (without any conversion) in a C object pointer. The + C program thus receives the actual object that was passed. The object's + reference count is not increased. The pointer stored is not *NULL*. ``O!`` (object) [*typeobject*, PyObject \*] Store a Python object in a C object pointer. This is similar to ``O``, but - takes two C arguments: the first is the address of a Python type object, the - second is the address of the C variable (of type :ctype:`PyObject\*`) into which - the object pointer is stored. If the Python object does not have the required - type, :exc:`TypeError` is raised. + takes two C arguments: the first is the address of a Python type object, + the second is the address of the C variable (of type :ctype:`PyObject\*`) + into which the object pointer is stored. If the Python object does not + have the required type, :exc:`TypeError` is raised. ``O&`` (object) [*converter*, *anything*] - Convert a Python object to a C variable through a *converter* function. This - takes two arguments: the first is a function, the second is the address of a C - variable (of arbitrary type), converted to :ctype:`void \*`. The *converter* - function in turn is called as follows:: + Convert a Python object to a C variable through a *converter* function. + This takes two arguments: the first is a function, the second is the + address of a C variable (of arbitrary type), converted to :ctype:`void \*`. + The *converter* function in turn is called as follows:: status = converter(object, address); where *object* is the Python object to be converted and *address* is the - :ctype:`void\*` argument that was passed to the :cfunc:`PyArg_Parse\*` function. - The returned *status* should be ``1`` for a successful conversion and ``0`` if - the conversion has failed. When the conversion fails, the *converter* function - should raise an exception and leave the content of *address* unmodified. + :ctype:`void\*` argument that was passed to the :cfunc:`PyArg_Parse\*` + function. The returned *status* should be ``1`` for a successful + conversion and ``0`` if the conversion has failed. When the conversion + fails, the *converter* function should raise an exception and leave the + content of *address* unmodified. ``S`` (string) [PyStringObject \*] Like ``O`` but requires that the Python object is a string object. Raises - :exc:`TypeError` if the object is not a string object. The C variable may also - be declared as :ctype:`PyObject\*`. + :exc:`TypeError` if the object is not a string object. The C variable may + also be declared as :ctype:`PyObject\*`. ``U`` (Unicode string) [PyUnicodeObject \*] Like ``O`` but requires that the Python object is a Unicode object. Raises - :exc:`TypeError` if the object is not a Unicode object. The C variable may also - be declared as :ctype:`PyObject\*`. + :exc:`TypeError` if the object is not a Unicode object. The C variable may + also be declared as :ctype:`PyObject\*`. ``t#`` (read-only character buffer) [char \*, int] Like ``s#``, but accepts any object which implements the read-only buffer - interface. The :ctype:`char\*` variable is set to point to the first byte of - the buffer, and the :ctype:`int` is set to the length of the buffer. Only - single-segment buffer objects are accepted; :exc:`TypeError` is raised for all - others. + interface. The :ctype:`char\*` variable is set to point to the first byte + of the buffer, and the :ctype:`int` is set to the length of the buffer. + Only single-segment buffer objects are accepted; :exc:`TypeError` is raised + for all others. ``w`` (read-write character buffer) [char \*] - Similar to ``s``, but accepts any object which implements the read-write buffer - interface. The caller must determine the length of the buffer by other means, - or use ``w#`` instead. Only single-segment buffer objects are accepted; - :exc:`TypeError` is raised for all others. + Similar to ``s``, but accepts any object which implements the read-write + buffer interface. The caller must determine the length of the buffer by + other means, or use ``w#`` instead. Only single-segment buffer objects are + accepted; :exc:`TypeError` is raised for all others. ``w#`` (read-write character buffer) [char \*, Py_ssize_t] Like ``s#``, but accepts any object which implements the read-write buffer - interface. The :ctype:`char \*` variable is set to point to the first byte of - the buffer, and the :ctype:`int` is set to the length of the buffer. Only - single-segment buffer objects are accepted; :exc:`TypeError` is raised for all - others. + interface. The :ctype:`char \*` variable is set to point to the first byte + of the buffer, and the :ctype:`int` is set to the length of the buffer. + Only single-segment buffer objects are accepted; :exc:`TypeError` is raised + for all others. ``w*`` (read-write byte-oriented buffer) [Py_buffer \*] This is to ``w`` what ``s*`` is to ``s``. @@ -265,72 +272,72 @@ variable(s) whose address should be passed. .. versionadded:: 2.6 ``(items)`` (tuple) [*matching-items*] - The object must be a Python sequence whose length is the number of format units - in *items*. The C arguments must correspond to the individual format units in - *items*. Format units for sequences may be nested. + The object must be a Python sequence whose length is the number of format + units in *items*. The C arguments must correspond to the individual format + units in *items*. Format units for sequences may be nested. .. note:: - Prior to Python version 1.5.2, this format specifier only accepted a tuple - containing the individual parameters, not an arbitrary sequence. Code which - previously caused :exc:`TypeError` to be raised here may now proceed without an - exception. This is not expected to be a problem for existing code. + Prior to Python version 1.5.2, this format specifier only accepted a + tuple containing the individual parameters, not an arbitrary sequence. + Code which previously caused :exc:`TypeError` to be raised here may now + proceed without an exception. This is not expected to be a problem for + existing code. It is possible to pass Python long integers where integers are requested; however no proper range checking is done --- the most significant bits are silently truncated when the receiving field is too small to receive the value -(actually, the semantics are inherited from downcasts in C --- your mileage may -vary). +(actually, the semantics are inherited from downcasts in C --- your mileage +may vary). A few other characters have a meaning in a format string. These may not occur inside nested parentheses. They are: ``|`` - Indicates that the remaining arguments in the Python argument list are optional. - The C variables corresponding to optional arguments should be initialized to - their default value --- when an optional argument is not specified, - :cfunc:`PyArg_ParseTuple` does not touch the contents of the corresponding C - variable(s). + Indicates that the remaining arguments in the Python argument list are + optional. The C variables corresponding to optional arguments should be + initialized to their default value --- when an optional argument is not + specified, :cfunc:`PyArg_ParseTuple` does not touch the contents of the + corresponding C variable(s). ``:`` - The list of format units ends here; the string after the colon is used as the - function name in error messages (the "associated value" of the exception that - :cfunc:`PyArg_ParseTuple` raises). + The list of format units ends here; the string after the colon is used as + the function name in error messages (the "associated value" of the + exception that :cfunc:`PyArg_ParseTuple` raises). ``;`` - The list of format units ends here; the string after the semicolon is used as - the error message *instead* of the default error message. ``:`` and ``;`` - mutually exclude each other. + The list of format units ends here; the string after the semicolon is used + as the error message *instead* of the default error message. ``:`` and + ``;`` mutually exclude each other. Note that any Python object references which are provided to the caller are *borrowed* references; do not decrement their reference count! Additional arguments passed to these functions must be addresses of variables whose type is determined by the format string; these are used to store values -from the input tuple. There are a few cases, as described in the list of format -units above, where these parameters are used as input values; they should match -what is specified for the corresponding format unit in that case. - -For the conversion to succeed, the *arg* object must match the format -and the format must be exhausted. On success, the -:cfunc:`PyArg_Parse\*` functions return true, otherwise they return -false and raise an appropriate exception. When the -:cfunc:`PyArg_Parse\*` functions fail due to conversion failure in one -of the format units, the variables at the addresses corresponding to that +from the input tuple. There are a few cases, as described in the list of +format units above, where these parameters are used as input values; they +should match what is specified for the corresponding format unit in that case. + +For the conversion to succeed, the *arg* object must match the format and the +format must be exhausted. On success, the :cfunc:`PyArg_Parse\*` functions +return true, otherwise they return false and raise an appropriate exception. +When the :cfunc:`PyArg_Parse\*` functions fail due to conversion failure in +one of the format units, the variables at the addresses corresponding to that and the following format units are left untouched. .. cfunction:: int PyArg_ParseTuple(PyObject *args, const char *format, ...) - Parse the parameters of a function that takes only positional parameters into - local variables. Returns true on success; on failure, it returns false and - raises the appropriate exception. + Parse the parameters of a function that takes only positional parameters + into local variables. Returns true on success; on failure, it returns + false and raises the appropriate exception. .. cfunction:: int PyArg_VaParse(PyObject *args, const char *format, va_list vargs) - Identical to :cfunc:`PyArg_ParseTuple`, except that it accepts a va_list rather - than a variable number of arguments. + Identical to :cfunc:`PyArg_ParseTuple`, except that it accepts a va_list + rather than a variable number of arguments. .. cfunction:: int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], ...) @@ -348,32 +355,33 @@ and the following format units are left untouched. .. cfunction:: int PyArg_Parse(PyObject *args, const char *format, ...) - Function used to deconstruct the argument lists of "old-style" functions --- - these are functions which use the :const:`METH_OLDARGS` parameter parsing - method. This is not recommended for use in parameter parsing in new code, and - most code in the standard interpreter has been modified to no longer use this - for that purpose. It does remain a convenient way to decompose other tuples, - however, and may continue to be used for that purpose. + Function used to deconstruct the argument lists of "old-style" functions + --- these are functions which use the :const:`METH_OLDARGS` parameter + parsing method. This is not recommended for use in parameter parsing in + new code, and most code in the standard interpreter has been modified to no + longer use this for that purpose. It does remain a convenient way to + decompose other tuples, however, and may continue to be used for that + purpose. .. cfunction:: int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...) A simpler form of parameter retrieval which does not use a format string to - specify the types of the arguments. Functions which use this method to retrieve - their parameters should be declared as :const:`METH_VARARGS` in function or - method tables. The tuple containing the actual parameters should be passed as - *args*; it must actually be a tuple. The length of the tuple must be at least - *min* and no more than *max*; *min* and *max* may be equal. Additional - arguments must be passed to the function, each of which should be a pointer to a - :ctype:`PyObject\*` variable; these will be filled in with the values from - *args*; they will contain borrowed references. The variables which correspond - to optional parameters not given by *args* will not be filled in; these should - be initialized by the caller. This function returns true on success and false if - *args* is not a tuple or contains the wrong number of elements; an exception - will be set if there was a failure. - - This is an example of the use of this function, taken from the sources for the - :mod:`_weakref` helper module for weak references:: + specify the types of the arguments. Functions which use this method to + retrieve their parameters should be declared as :const:`METH_VARARGS` in + function or method tables. The tuple containing the actual parameters + should be passed as *args*; it must actually be a tuple. The length of the + tuple must be at least *min* and no more than *max*; *min* and *max* may be + equal. Additional arguments must be passed to the function, each of which + should be a pointer to a :ctype:`PyObject\*` variable; these will be filled + in with the values from *args*; they will contain borrowed references. The + variables which correspond to optional parameters not given by *args* will + not be filled in; these should be initialized by the caller. This function + returns true on success and false if *args* is not a tuple or contains the + wrong number of elements; an exception will be set if there was a failure. + + This is an example of the use of this function, taken from the sources for + the :mod:`_weakref` helper module for weak references:: static PyObject * weakref_ref(PyObject *self, PyObject *args) @@ -388,8 +396,8 @@ and the following format units are left untouched. return result; } - The call to :cfunc:`PyArg_UnpackTuple` in this example is entirely equivalent to - this call to :cfunc:`PyArg_ParseTuple`:: + The call to :cfunc:`PyArg_UnpackTuple` in this example is entirely + equivalent to this call to :cfunc:`PyArg_ParseTuple`:: PyArg_ParseTuple(args, "O|O:ref", &object, &callback) @@ -398,40 +406,42 @@ and the following format units are left untouched. .. cfunction:: PyObject* Py_BuildValue(const char *format, ...) - Create a new value based on a format string similar to those accepted by the - :cfunc:`PyArg_Parse\*` family of functions and a sequence of values. Returns - the value or *NULL* in the case of an error; an exception will be raised if - *NULL* is returned. - - :cfunc:`Py_BuildValue` does not always build a tuple. It builds a tuple only if - its format string contains two or more format units. If the format string is - empty, it returns ``None``; if it contains exactly one format unit, it returns - whatever object is described by that format unit. To force it to return a tuple - of size 0 or one, parenthesize the format string. - - When memory buffers are passed as parameters to supply data to build objects, as - for the ``s`` and ``s#`` formats, the required data is copied. Buffers provided - by the caller are never referenced by the objects created by - :cfunc:`Py_BuildValue`. In other words, if your code invokes :cfunc:`malloc` - and passes the allocated memory to :cfunc:`Py_BuildValue`, your code is - responsible for calling :cfunc:`free` for that memory once + Create a new value based on a format string similar to those accepted by + the :cfunc:`PyArg_Parse\*` family of functions and a sequence of values. + Returns the value or *NULL* in the case of an error; an exception will be + raised if *NULL* is returned. + + :cfunc:`Py_BuildValue` does not always build a tuple. It builds a tuple + only if its format string contains two or more format units. If the format + string is empty, it returns ``None``; if it contains exactly one format + unit, it returns whatever object is described by that format unit. To + force it to return a tuple of size 0 or one, parenthesize the format + string. + + When memory buffers are passed as parameters to supply data to build + objects, as for the ``s`` and ``s#`` formats, the required data is copied. + Buffers provided by the caller are never referenced by the objects created + by :cfunc:`Py_BuildValue`. In other words, if your code invokes + :cfunc:`malloc` and passes the allocated memory to :cfunc:`Py_BuildValue`, + your code is responsible for calling :cfunc:`free` for that memory once :cfunc:`Py_BuildValue` returns. - In the following description, the quoted form is the format unit; the entry in - (round) parentheses is the Python object type that the format unit will return; - and the entry in [square] brackets is the type of the C value(s) to be passed. + In the following description, the quoted form is the format unit; the entry + in (round) parentheses is the Python object type that the format unit will + return; and the entry in [square] brackets is the type of the C value(s) to + be passed. - The characters space, tab, colon and comma are ignored in format strings (but - not within format units such as ``s#``). This can be used to make long format - strings a tad more readable. + The characters space, tab, colon and comma are ignored in format strings + (but not within format units such as ``s#``). This can be used to make + long format strings a tad more readable. ``s`` (string) [char \*] - Convert a null-terminated C string to a Python object. If the C string pointer - is *NULL*, ``None`` is used. + Convert a null-terminated C string to a Python object. If the C string + pointer is *NULL*, ``None`` is used. ``s#`` (string) [char \*, int] - Convert a C string and its length to a Python object. If the C string pointer - is *NULL*, the length is ignored and ``None`` is returned. + Convert a C string and its length to a Python object. If the C string + pointer is *NULL*, the length is ignored and ``None`` is returned. ``z`` (string or ``None``) [char \*] Same as ``s``. @@ -440,13 +450,14 @@ and the following format units are left untouched. Same as ``s#``. ``u`` (Unicode string) [Py_UNICODE \*] - Convert a null-terminated buffer of Unicode (UCS-2 or UCS-4) data to a Python - Unicode object. If the Unicode buffer pointer is *NULL*, ``None`` is returned. + Convert a null-terminated buffer of Unicode (UCS-2 or UCS-4) data to a + Python Unicode object. If the Unicode buffer pointer is *NULL*, + ``None`` is returned. ``u#`` (Unicode string) [Py_UNICODE \*, int] - Convert a Unicode (UCS-2 or UCS-4) data buffer and its length to a Python - Unicode object. If the Unicode buffer pointer is *NULL*, the length is ignored - and ``None`` is returned. + Convert a Unicode (UCS-2 or UCS-4) data buffer and its length to a + Python Unicode object. If the Unicode buffer pointer is *NULL*, the + length is ignored and ``None`` is returned. ``i`` (integer) [int] Convert a plain C :ctype:`int` to a Python integer object. @@ -467,20 +478,20 @@ and the following format units are left untouched. Convert a C :ctype:`unsigned short int` to a Python integer object. ``I`` (integer/long) [unsigned int] - Convert a C :ctype:`unsigned int` to a Python integer object or a Python long - integer object, if it is larger than ``sys.maxint``. + Convert a C :ctype:`unsigned int` to a Python integer object or a Python + long integer object, if it is larger than ``sys.maxint``. ``k`` (integer/long) [unsigned long] - Convert a C :ctype:`unsigned long` to a Python integer object or a Python long - integer object, if it is larger than ``sys.maxint``. + Convert a C :ctype:`unsigned long` to a Python integer object or a + Python long integer object, if it is larger than ``sys.maxint``. ``L`` (long) [PY_LONG_LONG] - Convert a C :ctype:`long long` to a Python long integer object. Only available - on platforms that support :ctype:`long long`. + Convert a C :ctype:`long long` to a Python long integer object. Only + available on platforms that support :ctype:`long long`. ``K`` (long) [unsigned PY_LONG_LONG] - Convert a C :ctype:`unsigned long long` to a Python long integer object. Only - available on platforms that support :ctype:`unsigned long long`. + Convert a C :ctype:`unsigned long long` to a Python long integer object. + Only available on platforms that support :ctype:`unsigned long long`. ``n`` (int) [Py_ssize_t] Convert a C :ctype:`Py_ssize_t` to a Python integer or long integer. @@ -488,8 +499,8 @@ and the following format units are left untouched. .. versionadded:: 2.5 ``c`` (string of length 1) [char] - Convert a C :ctype:`int` representing a character to a Python string of length - 1. + Convert a C :ctype:`int` representing a character to a Python string of + length 1. ``d`` (float) [double] Convert a C :ctype:`double` to a Python floating point number. @@ -502,39 +513,41 @@ and the following format units are left untouched. ``O`` (object) [PyObject \*] Pass a Python object untouched (except for its reference count, which is - incremented by one). If the object passed in is a *NULL* pointer, it is assumed - that this was caused because the call producing the argument found an error and - set an exception. Therefore, :cfunc:`Py_BuildValue` will return *NULL* but won't - raise an exception. If no exception has been raised yet, :exc:`SystemError` is - set. + incremented by one). If the object passed in is a *NULL* pointer, it is + assumed that this was caused because the call producing the argument + found an error and set an exception. Therefore, :cfunc:`Py_BuildValue` + will return *NULL* but won't raise an exception. If no exception has + been raised yet, :exc:`SystemError` is set. ``S`` (object) [PyObject \*] Same as ``O``. ``N`` (object) [PyObject \*] - Same as ``O``, except it doesn't increment the reference count on the object. - Useful when the object is created by a call to an object constructor in the - argument list. + Same as ``O``, except it doesn't increment the reference count on the + object. Useful when the object is created by a call to an object + constructor in the argument list. ``O&`` (object) [*converter*, *anything*] - Convert *anything* to a Python object through a *converter* function. The - function is called with *anything* (which should be compatible with :ctype:`void - \*`) as its argument and should return a "new" Python object, or *NULL* if an - error occurred. + Convert *anything* to a Python object through a *converter* function. + The function is called with *anything* (which should be compatible with + :ctype:`void \*`) as its argument and should return a "new" Python + object, or *NULL* if an error occurred. ``(items)`` (tuple) [*matching-items*] - Convert a sequence of C values to a Python tuple with the same number of items. + Convert a sequence of C values to a Python tuple with the same number of + items. ``[items]`` (list) [*matching-items*] - Convert a sequence of C values to a Python list with the same number of items. + Convert a sequence of C values to a Python list with the same number of + items. ``{items}`` (dictionary) [*matching-items*] - Convert a sequence of C values to a Python dictionary. Each pair of consecutive - C values adds one item to the dictionary, serving as key and value, - respectively. + Convert a sequence of C values to a Python dictionary. Each pair of + consecutive C values adds one item to the dictionary, serving as key and + value, respectively. - If there is an error in the format string, the :exc:`SystemError` exception is - set and *NULL* returned. + If there is an error in the format string, the :exc:`SystemError` exception + is set and *NULL* returned. .. cfunction:: PyObject* Py_VaBuildValue(const char *format, va_list vargs) |