From 7974b0f2d8a91b4b2783e8bb93b8b809de833cf1 Mon Sep 17 00:00:00 2001 From: Guido van Rossum Date: Sun, 5 Oct 1997 18:53:00 +0000 Subject: Documented __import__, callable, isinstance, issubclass, and slice. --- Doc/lib/libfuncs.tex | 88 +++++++++++++++++++++++++++++++++++++++++++++++++--- Doc/libfuncs.tex | 88 +++++++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 166 insertions(+), 10 deletions(-) diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex index 0ef8201..0211cec 100644 --- a/Doc/lib/libfuncs.tex +++ b/Doc/lib/libfuncs.tex @@ -5,10 +5,51 @@ are always available. They are listed here in alphabetical order. \renewcommand{\indexsubitem}{(built-in function)} + +\begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}} +This function is invoked by the \code{import} statement. It +mainly exists so that you can replace it with another +function that has a compatible interface, in order to change the +semantics of the \code{import} statement. For examples of why and +how you would do this, see the standard library modules \code{ni}, +\code{ihooks} and \code{rexec}. See also the built-in module +\code{imp}, which defines some useful operations out of which you can +build your own \code{__import__} function. +\stindex{import} +\stmodindex{ni} +\stmodindex{ihooks} +\stmodindex{rexec} +\bimodindex{imp} + +For example, the statement \code{import spam} results in the following +call: +\code{__import__('spam', globals(), locals(), [])}; +the statement \code{from spam.ham import eggs} results in +\code{__import__('spam.ham', globals(), locals(), ['eggs'])}. +Note that even though \code{locals()} and \code{['eggs']} are passed +in as arguments, the \code{__import__()} function does not set the +local variable named \code{eggs}; this is done by subsequent code that +is generated for the import statement. (In fact, the standard +implementation does not use its \var{locals} argument at all, and uses +its \var{globals} only to determine the package context of the +\code{import} statement.) + +When the \var{name} variable is of the form \code{package.module}, +normally, the top-level package (the name up till the first dot) is +returned, \emph{not} the module named by \var{name}. However, when a +non-empty \var{fromlist} argument is given, the module named by +\var{name} is returned. This is done for compatibility with the +bytecode generated for the different kinds of import statement; when +using \code{import spam.ham.eggs}, the top-level package \code{spam} +must be placed in the importing namespace, but when using \code{from +spam.ham import eggs}, the \code{spam.ham} subpackage must be used to +find the \code{eggs} variable. +\end{funcdesc} + \begin{funcdesc}{abs}{x} Return the absolute value of a number. The argument may be a plain or long integer or a floating point number. If the argument is a - complex number, its magnitude is returned. + complex number, its magnitude is returned. \end{funcdesc} \begin{funcdesc}{apply}{function\, args\optional{, keywords}} @@ -24,6 +65,14 @@ dictionary whose keys are strings. It specifies keyword arguments to be added to the end of the the argument list. \end{funcdesc} +\begin{funcdesc}{callable}{object} +Return true if the \var{object} argument appears callable, false if +not. If this returns true, it is still possible that a call fails, +but if it is false, calling \var{object} will never succeed. Note +that classes are callable (calling a class returns a new instance); +class instances are callable if they have an attribute \code{__call__}. +\end{funcdesc} + \begin{funcdesc}{chr}{i} Return a string of one character whose \ASCII{} code is the integer \var{i}, e.g., \code{chr(97)} returns the string \code{'a'}. This is the @@ -76,6 +125,9 @@ be added to the end of the the argument list. \end{funcdesc} \begin{funcdesc}{dir}{} +XXX New functionality takes anything and looks in __dict__, +__methods__, __members__. + Without arguments, return the list of names in the current local symbol table. With a module, class or class instance object as argument (or anything else that has a \code{__dict__} attribute), @@ -253,6 +305,20 @@ module from which it is called). language definition should require truncation towards zero.} \end{funcdesc} +\begin{funcdesc}{isinstance}{object, class} +Return true if the \var{object} argument is an instance of the +\var{class} argument, or of a (direct or indirect) subclass thereof. +If \var{object} is not a class instance, the function always returns +false. If \var{class} is not a class object, a \code{TypeError} +exception is raised. +\end{funcdesc} + +\begin{funcdesc}{issubclass}{class1, class2} +Return true if \var{class1} is a subclass (direct or indirect) of +\var{class2}. A class is considered a subclass of itself. If either +argument is not a class object, a \code{TypeError} exception is raised. +\end{funcdesc} + \begin{funcdesc}{len}{s} Return the length (the number of items) of an object. The argument may be a sequence (string, tuple or list) or a mapping (dictionary). @@ -365,7 +431,7 @@ there's no reliable way to determine whether this is the case.} 35000)} is not allowed. \end{funcdesc} -\begin{funcdesc}{range}{\optional{start\,} end\optional{\, step}} +\begin{funcdesc}{range}{\optional{start\,} stop\optional{\, step}} This is a versatile function to create lists containing arithmetic progressions. It is most often used in \code{for} loops. The arguments must be plain integers. If the \var{step} argument is @@ -374,9 +440,9 @@ there's no reliable way to determine whether this is the case.} plain integers \code{[\var{start}, \var{start} + \var{step}, \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, the last element is the largest \code{\var{start} + \var{i} * - \var{step}} less than \var{end}; if \var{step} is negative, the last + \var{step}} less than \var{stop}; if \var{step} is negative, the last element is the largest \code{\var{start} + \var{i} * \var{step}} - greater than \var{end}. \var{step} must not be zero (or else an + greater than \var{stop}. \var{step} must not be zero (or else an exception is raised). Example: \bcode\begin{verbatim} @@ -499,6 +565,18 @@ when passed to \code{eval()}. \code{\var{x}.\var{foobar} = 123}. \end{funcdesc} +\begin{funcdesc}{slice}{\optional{start\,} stop\optional{\, step}} +Return a slice object representing the set of indices specified by +\code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} +and \var{step} arguments default to None. Slice objects have +read-only data attributes \code{start}, \code{stop} and \code{step} +which merely return the argument values (or their default). They have +no other explicit functionality; however they are used by Numerical +Python and other third party extensions. Slice objects are also +generated when extended indexing syntax is used, e.g. for +\code{a[start:stop:step]} or \code{a[start:stop, i]}. +\end{funcdesc} + \begin{funcdesc}{str}{object} Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference @@ -541,7 +619,7 @@ cannot normally be affected this way, but variables retrieved from other scopes (e.g. modules) can be. This may change.} \end{funcdesc} -\begin{funcdesc}{xrange}{\optional{start\,} end\optional{\, step}} +\begin{funcdesc}{xrange}{\optional{start\,} stop\optional{\, step}} This function is very similar to \code{range()}, but returns an ``xrange object'' instead of a list. This is an opaque sequence type which yields the same values as the corresponding list, without diff --git a/Doc/libfuncs.tex b/Doc/libfuncs.tex index 0ef8201..0211cec 100644 --- a/Doc/libfuncs.tex +++ b/Doc/libfuncs.tex @@ -5,10 +5,51 @@ are always available. They are listed here in alphabetical order. \renewcommand{\indexsubitem}{(built-in function)} + +\begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}} +This function is invoked by the \code{import} statement. It +mainly exists so that you can replace it with another +function that has a compatible interface, in order to change the +semantics of the \code{import} statement. For examples of why and +how you would do this, see the standard library modules \code{ni}, +\code{ihooks} and \code{rexec}. See also the built-in module +\code{imp}, which defines some useful operations out of which you can +build your own \code{__import__} function. +\stindex{import} +\stmodindex{ni} +\stmodindex{ihooks} +\stmodindex{rexec} +\bimodindex{imp} + +For example, the statement \code{import spam} results in the following +call: +\code{__import__('spam', globals(), locals(), [])}; +the statement \code{from spam.ham import eggs} results in +\code{__import__('spam.ham', globals(), locals(), ['eggs'])}. +Note that even though \code{locals()} and \code{['eggs']} are passed +in as arguments, the \code{__import__()} function does not set the +local variable named \code{eggs}; this is done by subsequent code that +is generated for the import statement. (In fact, the standard +implementation does not use its \var{locals} argument at all, and uses +its \var{globals} only to determine the package context of the +\code{import} statement.) + +When the \var{name} variable is of the form \code{package.module}, +normally, the top-level package (the name up till the first dot) is +returned, \emph{not} the module named by \var{name}. However, when a +non-empty \var{fromlist} argument is given, the module named by +\var{name} is returned. This is done for compatibility with the +bytecode generated for the different kinds of import statement; when +using \code{import spam.ham.eggs}, the top-level package \code{spam} +must be placed in the importing namespace, but when using \code{from +spam.ham import eggs}, the \code{spam.ham} subpackage must be used to +find the \code{eggs} variable. +\end{funcdesc} + \begin{funcdesc}{abs}{x} Return the absolute value of a number. The argument may be a plain or long integer or a floating point number. If the argument is a - complex number, its magnitude is returned. + complex number, its magnitude is returned. \end{funcdesc} \begin{funcdesc}{apply}{function\, args\optional{, keywords}} @@ -24,6 +65,14 @@ dictionary whose keys are strings. It specifies keyword arguments to be added to the end of the the argument list. \end{funcdesc} +\begin{funcdesc}{callable}{object} +Return true if the \var{object} argument appears callable, false if +not. If this returns true, it is still possible that a call fails, +but if it is false, calling \var{object} will never succeed. Note +that classes are callable (calling a class returns a new instance); +class instances are callable if they have an attribute \code{__call__}. +\end{funcdesc} + \begin{funcdesc}{chr}{i} Return a string of one character whose \ASCII{} code is the integer \var{i}, e.g., \code{chr(97)} returns the string \code{'a'}. This is the @@ -76,6 +125,9 @@ be added to the end of the the argument list. \end{funcdesc} \begin{funcdesc}{dir}{} +XXX New functionality takes anything and looks in __dict__, +__methods__, __members__. + Without arguments, return the list of names in the current local symbol table. With a module, class or class instance object as argument (or anything else that has a \code{__dict__} attribute), @@ -253,6 +305,20 @@ module from which it is called). language definition should require truncation towards zero.} \end{funcdesc} +\begin{funcdesc}{isinstance}{object, class} +Return true if the \var{object} argument is an instance of the +\var{class} argument, or of a (direct or indirect) subclass thereof. +If \var{object} is not a class instance, the function always returns +false. If \var{class} is not a class object, a \code{TypeError} +exception is raised. +\end{funcdesc} + +\begin{funcdesc}{issubclass}{class1, class2} +Return true if \var{class1} is a subclass (direct or indirect) of +\var{class2}. A class is considered a subclass of itself. If either +argument is not a class object, a \code{TypeError} exception is raised. +\end{funcdesc} + \begin{funcdesc}{len}{s} Return the length (the number of items) of an object. The argument may be a sequence (string, tuple or list) or a mapping (dictionary). @@ -365,7 +431,7 @@ there's no reliable way to determine whether this is the case.} 35000)} is not allowed. \end{funcdesc} -\begin{funcdesc}{range}{\optional{start\,} end\optional{\, step}} +\begin{funcdesc}{range}{\optional{start\,} stop\optional{\, step}} This is a versatile function to create lists containing arithmetic progressions. It is most often used in \code{for} loops. The arguments must be plain integers. If the \var{step} argument is @@ -374,9 +440,9 @@ there's no reliable way to determine whether this is the case.} plain integers \code{[\var{start}, \var{start} + \var{step}, \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, the last element is the largest \code{\var{start} + \var{i} * - \var{step}} less than \var{end}; if \var{step} is negative, the last + \var{step}} less than \var{stop}; if \var{step} is negative, the last element is the largest \code{\var{start} + \var{i} * \var{step}} - greater than \var{end}. \var{step} must not be zero (or else an + greater than \var{stop}. \var{step} must not be zero (or else an exception is raised). Example: \bcode\begin{verbatim} @@ -499,6 +565,18 @@ when passed to \code{eval()}. \code{\var{x}.\var{foobar} = 123}. \end{funcdesc} +\begin{funcdesc}{slice}{\optional{start\,} stop\optional{\, step}} +Return a slice object representing the set of indices specified by +\code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} +and \var{step} arguments default to None. Slice objects have +read-only data attributes \code{start}, \code{stop} and \code{step} +which merely return the argument values (or their default). They have +no other explicit functionality; however they are used by Numerical +Python and other third party extensions. Slice objects are also +generated when extended indexing syntax is used, e.g. for +\code{a[start:stop:step]} or \code{a[start:stop, i]}. +\end{funcdesc} + \begin{funcdesc}{str}{object} Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference @@ -541,7 +619,7 @@ cannot normally be affected this way, but variables retrieved from other scopes (e.g. modules) can be. This may change.} \end{funcdesc} -\begin{funcdesc}{xrange}{\optional{start\,} end\optional{\, step}} +\begin{funcdesc}{xrange}{\optional{start\,} stop\optional{\, step}} This function is very similar to \code{range()}, but returns an ``xrange object'' instead of a list. This is an opaque sequence type which yields the same values as the corresponding list, without -- cgit v0.12