1994-01-02 01:22:07 +00:00
|
|
|
\section{Built-in Functions}
|
1997-12-16 04:06:33 +00:00
|
|
|
\label{built-in-funcs}
|
1994-01-02 01:22:07 +00:00
|
|
|
|
|
|
|
The Python interpreter has a number of functions built into it that
|
|
|
|
are always available. They are listed here in alphabetical order.
|
|
|
|
|
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\setindexsubitem{(built-in function)}
|
1997-10-05 18:53:00 +00:00
|
|
|
|
|
|
|
\begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}}
|
1998-03-03 21:56:15 +00:00
|
|
|
This function is invoked by the \keyword{import} statement. It
|
1997-10-05 18:53:00 +00:00
|
|
|
mainly exists so that you can replace it with another
|
|
|
|
function that has a compatible interface, in order to change the
|
1998-03-03 21:56:15 +00:00
|
|
|
semantics of the \keyword{import} statement. For examples of why and
|
1998-04-02 18:46:44 +00:00
|
|
|
how you would do this, see the standard library modules
|
1998-03-03 21:56:15 +00:00
|
|
|
\module{ihooks} and \module{rexec}. See also the built-in module
|
|
|
|
\module{imp}, which defines some useful operations out of which you can
|
|
|
|
build your own \function{__import__()} function.
|
1997-10-05 18:53:00 +00:00
|
|
|
\stindex{import}
|
1997-12-15 22:28:38 +00:00
|
|
|
\refstmodindex{ihooks}
|
|
|
|
\refstmodindex{rexec}
|
|
|
|
\refbimodindex{imp}
|
1997-10-05 18:53:00 +00:00
|
|
|
|
1998-03-03 21:56:15 +00:00
|
|
|
For example, the statement `\code{import} \code{spam}' results in the
|
1998-02-13 21:26:35 +00:00
|
|
|
following call:
|
|
|
|
\code{__import__('spam',} \code{globals(),} \code{locals(), [])};
|
|
|
|
the statement \code{from} \code{spam.ham import} \code{eggs} results
|
|
|
|
in \code{__import__('spam.ham',} \code{globals(),} \code{locals(),}
|
|
|
|
\code{['eggs'])}.
|
1997-10-05 18:53:00 +00:00
|
|
|
Note that even though \code{locals()} and \code{['eggs']} are passed
|
1998-03-03 21:56:15 +00:00
|
|
|
in as arguments, the \function{__import__()} function does not set the
|
1997-10-05 18:53:00 +00:00
|
|
|
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
|
1998-03-03 21:56:15 +00:00
|
|
|
\keyword{import} statement.)
|
1997-10-05 18:53:00 +00:00
|
|
|
|
|
|
|
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
|
1998-03-03 21:56:15 +00:00
|
|
|
using \samp{import spam.ham.eggs}, the top-level package \code{spam}
|
|
|
|
must be placed in the importing namespace, but when using \samp{from
|
1997-10-05 18:53:00 +00:00
|
|
|
spam.ham import eggs}, the \code{spam.ham} subpackage must be used to
|
|
|
|
find the \code{eggs} variable.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\begin{funcdesc}{abs}{x}
|
|
|
|
Return the absolute value of a number. The argument may be a plain
|
1997-06-02 17:21:20 +00:00
|
|
|
or long integer or a floating point number. If the argument is a
|
1997-10-05 18:53:00 +00:00
|
|
|
complex number, its magnitude is returned.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{apply}{function, args\optional{, keywords}}
|
1994-01-02 01:22:07 +00:00
|
|
|
The \var{function} argument must be a callable object (a user-defined or
|
|
|
|
built-in function or method, or a class object) and the \var{args}
|
|
|
|
argument must be a tuple. The \var{function} is called with
|
|
|
|
\var{args} as argument list; the number of arguments is the the length
|
|
|
|
of the tuple. (This is different from just calling
|
|
|
|
\code{\var{func}(\var{args})}, since in that case there is always
|
|
|
|
exactly one argument.)
|
1995-10-08 01:06:46 +00:00
|
|
|
If the optional \var{keywords} argument is present, it must be a
|
|
|
|
dictionary whose keys are strings. It specifies keyword arguments to
|
|
|
|
be added to the end of the the argument list.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1997-10-05 18:53:00 +00:00
|
|
|
\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);
|
1998-03-03 21:56:15 +00:00
|
|
|
class instances are callable if they have a \method{__call__()} method.
|
1997-10-05 18:53:00 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\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
|
1998-03-03 21:56:15 +00:00
|
|
|
inverse of \function{ord()}. The argument must be in the range [0..255],
|
1994-01-02 01:22:07 +00:00
|
|
|
inclusive.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{cmp}{x, y}
|
1994-01-02 01:22:07 +00:00
|
|
|
Compare the two objects \var{x} and \var{y} and return an integer
|
|
|
|
according to the outcome. The return value is negative if \code{\var{x}
|
|
|
|
< \var{y}}, zero if \code{\var{x} == \var{y}} and strictly positive if
|
|
|
|
\code{\var{x} > \var{y}}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{coerce}{x, y}
|
1994-01-02 01:22:07 +00:00
|
|
|
Return a tuple consisting of the two numeric arguments converted to
|
|
|
|
a common type, using the same rules as used by arithmetic
|
|
|
|
operations.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{compile}{string, filename, kind}
|
1994-01-02 01:22:07 +00:00
|
|
|
Compile the \var{string} into a code object. Code objects can be
|
1998-03-03 21:56:15 +00:00
|
|
|
executed by an \keyword{exec} statement or evaluated by a call to
|
|
|
|
\function{eval()}. The \var{filename} argument should
|
1994-01-02 01:22:07 +00:00
|
|
|
give the file from which the code was read; pass e.g. \code{'<string>'}
|
|
|
|
if it wasn't read from a file. The \var{kind} argument specifies
|
|
|
|
what kind of code must be compiled; it can be \code{'exec'} if
|
1995-07-07 22:58:28 +00:00
|
|
|
\var{string} consists of a sequence of statements, \code{'eval'}
|
|
|
|
if it consists of a single expression, or \code{'single'} if
|
|
|
|
it consists of a single interactive statement (in the latter case,
|
|
|
|
expression statements that evaluate to something else than
|
|
|
|
\code{None} will printed).
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1997-04-02 06:04:02 +00:00
|
|
|
\begin{funcdesc}{complex}{real\optional{, imag}}
|
|
|
|
Create a complex number with the value \var{real} + \var{imag}*j.
|
|
|
|
Each argument may be any numeric type (including complex).
|
|
|
|
If \var{imag} is omitted, it defaults to zero and the function
|
1998-03-03 21:56:15 +00:00
|
|
|
serves as a numeric conversion function like \function{int()},
|
|
|
|
\function{long()} and \function{float()}.
|
1997-04-02 06:04:02 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{delattr}{object, name}
|
1998-03-03 21:56:15 +00:00
|
|
|
This is a relative of \function{setattr()}. The arguments are an
|
1994-08-16 22:15:11 +00:00
|
|
|
object and a string. The string must be the name
|
|
|
|
of one of the object's attributes. The function deletes
|
|
|
|
the named attribute, provided the object allows it. For example,
|
1995-03-07 10:14:09 +00:00
|
|
|
\code{delattr(\var{x}, '\var{foobar}')} is equivalent to
|
1994-08-16 22:15:11 +00:00
|
|
|
\code{del \var{x}.\var{foobar}}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-04-16 22:10:27 +00:00
|
|
|
\begin{funcdesc}{dir}{\optional{object}}
|
1994-01-02 01:22:07 +00:00
|
|
|
Without arguments, return the list of names in the current local
|
1997-12-30 20:38:16 +00:00
|
|
|
symbol table. With an argument, attempts to return a list of valid
|
|
|
|
attribute for that object. This information is gleaned from the
|
1998-03-03 21:56:15 +00:00
|
|
|
object's \member{__dict__}, \member{__methods__} and \member{__members__}
|
1997-12-30 20:38:16 +00:00
|
|
|
attributes, if defined. The list is not necessarily complete; e.g.,
|
|
|
|
for classes, attributes defined in base classes are not included,
|
|
|
|
and for class instances, methods are not included.
|
|
|
|
The resulting list is sorted alphabetically. For example:
|
1994-01-02 01:22:07 +00:00
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\begin{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
>>> import sys
|
|
|
|
>>> dir()
|
|
|
|
['sys']
|
|
|
|
>>> dir(sys)
|
|
|
|
['argv', 'exit', 'modules', 'path', 'stderr', 'stdin', 'stdout']
|
|
|
|
>>>
|
1998-02-13 06:58:54 +00:00
|
|
|
\end{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{divmod}{a, b}
|
1997-12-30 20:38:16 +00:00
|
|
|
Take two numbers as arguments and return a pair of numbers consisting
|
|
|
|
of their quotient and remainder when using long division. With mixed
|
1994-01-02 01:22:07 +00:00
|
|
|
operand types, the rules for binary arithmetic operators apply. For
|
|
|
|
plain and long integers, the result is the same as
|
|
|
|
\code{(\var{a} / \var{b}, \var{a} \%{} \var{b})}.
|
|
|
|
For floating point numbers the result is the same as
|
|
|
|
\code{(math.floor(\var{a} / \var{b}), \var{a} \%{} \var{b})}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{eval}{expression\optional{, globals\optional{, locals}}}
|
1994-01-02 01:22:07 +00:00
|
|
|
The arguments are a string and two optional dictionaries. The
|
1995-01-10 10:50:24 +00:00
|
|
|
\var{expression} argument is parsed and evaluated as a Python
|
|
|
|
expression (technically speaking, a condition list) using the
|
|
|
|
\var{globals} and \var{locals} dictionaries as global and local name
|
1995-03-17 16:07:09 +00:00
|
|
|
space. If the \var{locals} dictionary is omitted it defaults to
|
|
|
|
the \var{globals} dictionary. If both dictionaries are omitted, the
|
1998-03-03 21:56:15 +00:00
|
|
|
expression is executed in the environment where \keyword{eval} is
|
1995-01-10 10:50:24 +00:00
|
|
|
called. The return value is the result of the evaluated expression.
|
|
|
|
Syntax errors are reported as exceptions. Example:
|
1994-01-02 01:22:07 +00:00
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\begin{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
>>> x = 1
|
|
|
|
>>> print eval('x+1')
|
|
|
|
2
|
1998-02-13 06:58:54 +00:00
|
|
|
\end{verbatim}
|
1998-03-03 21:56:15 +00:00
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
This function can also be used to execute arbitrary code objects
|
1998-03-03 21:56:15 +00:00
|
|
|
(e.g.\ created by \function{compile()}). In this case pass a code
|
1994-01-02 01:22:07 +00:00
|
|
|
object instead of a string. The code object must have been compiled
|
|
|
|
passing \code{'eval'} to the \var{kind} argument.
|
|
|
|
|
1995-03-07 10:14:09 +00:00
|
|
|
Hints: dynamic execution of statements is supported by the
|
1998-03-03 21:56:15 +00:00
|
|
|
\keyword{exec} statement. Execution of statements from a file is
|
|
|
|
supported by the \function{execfile()} function. The
|
|
|
|
\function{globals()} and \function{locals()} functions returns the
|
|
|
|
current global and local dictionary, respectively, which may be
|
|
|
|
useful to pass around for use by \function{eval()} or
|
|
|
|
\function{execfile()}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{execfile}{file\optional{, globals\optional{, locals}}}
|
1995-03-17 16:07:09 +00:00
|
|
|
This function is similar to the
|
1998-03-03 21:56:15 +00:00
|
|
|
\keyword{exec} statement, but parses a file instead of a string. It
|
|
|
|
is different from the \keyword{import} statement in that it does not
|
|
|
|
use the module administration --- it reads the file unconditionally
|
|
|
|
and does not create a new module.\footnote{It is used relatively
|
|
|
|
rarely so does not warrant being made into a statement.}
|
1995-01-10 10:50:24 +00:00
|
|
|
|
|
|
|
The arguments are a file name and two optional dictionaries. The
|
|
|
|
file is parsed and evaluated as a sequence of Python statements
|
|
|
|
(similarly to a module) using the \var{globals} and \var{locals}
|
1995-03-17 16:07:09 +00:00
|
|
|
dictionaries as global and local name space. If the \var{locals}
|
|
|
|
dictionary is omitted it defaults to the \var{globals} dictionary.
|
1995-01-10 10:50:24 +00:00
|
|
|
If both dictionaries are omitted, the expression is executed in the
|
1998-03-03 21:56:15 +00:00
|
|
|
environment where \function{execfile()} is called. The return value is
|
1995-03-17 16:07:09 +00:00
|
|
|
\code{None}.
|
1995-01-10 10:50:24 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{filter}{function, list}
|
1994-01-02 01:22:07 +00:00
|
|
|
Construct a list from those elements of \var{list} for which
|
|
|
|
\var{function} returns true. If \var{list} is a string or a tuple,
|
|
|
|
the result also has that type; otherwise it is always a list. If
|
|
|
|
\var{function} is \code{None}, the identity function is assumed,
|
1995-03-07 10:14:09 +00:00
|
|
|
i.e.\ all elements of \var{list} that are false (zero or empty) are
|
1994-01-02 01:22:07 +00:00
|
|
|
removed.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{float}{x}
|
1997-04-02 06:04:02 +00:00
|
|
|
Convert a string or a number to floating point. If the argument is a
|
|
|
|
string, it must contain a possibly singed decimal or floating point
|
|
|
|
number, possibly embedded in whitespace;
|
|
|
|
this behaves identical to \code{string.atof(\var{x})}.
|
|
|
|
Otherwise, the argument may be a plain or
|
|
|
|
long integer or a floating point number, and a floating point number
|
|
|
|
with the same value (within Python's floating point precision) is
|
|
|
|
returned.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{getattr}{object, name}
|
1994-01-02 01:22:07 +00:00
|
|
|
The arguments are an object and a string. The string must be the
|
1998-03-03 21:56:15 +00:00
|
|
|
name of one of the object's attributes. The result is the value of
|
|
|
|
that attribute. For example, \code{getattr(\var{x},
|
|
|
|
'\var{foobar}')} is equivalent to \code{\var{x}.\var{foobar}}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1995-07-07 22:58:28 +00:00
|
|
|
\begin{funcdesc}{globals}{}
|
|
|
|
Return a dictionary representing the current global symbol table.
|
|
|
|
This is always the dictionary of the current module (inside a
|
|
|
|
function or method, this is the module where it is defined, not the
|
|
|
|
module from which it is called).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{hasattr}{object, name}
|
1994-01-02 01:22:07 +00:00
|
|
|
The arguments are an object and a string. The result is 1 if the
|
|
|
|
string is the name of one of the object's attributes, 0 if not.
|
1998-03-03 21:56:15 +00:00
|
|
|
(This is implemented by calling \code{getattr(\var{object},
|
|
|
|
\var{name})} and seeing whether it raises an exception or not.)
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{hash}{object}
|
|
|
|
Return the hash value of the object (if it has one). Hash values
|
1997-12-30 20:38:16 +00:00
|
|
|
are integers. They are used to quickly compare dictionary
|
1994-01-02 01:22:07 +00:00
|
|
|
keys during a dictionary lookup. Numeric values that compare equal
|
|
|
|
have the same hash value (even if they are of different types, e.g.
|
|
|
|
1 and 1.0).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{hex}{x}
|
1995-03-17 16:07:09 +00:00
|
|
|
Convert an integer number (of any size) to a hexadecimal string.
|
1997-01-14 18:44:23 +00:00
|
|
|
The result is a valid Python expression. Note: this always yields
|
|
|
|
an unsigned literal, e.g. on a 32-bit machine, \code{hex(-1)} yields
|
|
|
|
\code{'0xffffffff'}. When evaluated on a machine with the same
|
|
|
|
word size, this literal is evaluated as -1; at a different word
|
|
|
|
size, it may turn up as a large positive number or raise an
|
1998-03-03 21:56:15 +00:00
|
|
|
\exception{OverflowError} exception.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{id}{object}
|
|
|
|
Return the `identity' of an object. This is an integer which is
|
|
|
|
guaranteed to be unique and constant for this object during its
|
|
|
|
lifetime. (Two objects whose lifetimes are disjunct may have the
|
1998-03-03 21:56:15 +00:00
|
|
|
same \function{id()} value.) (Implementation note: this is the
|
|
|
|
address of the object.)
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-08-08 12:30:22 +00:00
|
|
|
\begin{funcdesc}{input}{\optional{prompt}}
|
1998-06-17 15:16:40 +00:00
|
|
|
Equivalent to \code{eval(raw_input(\var{prompt}))}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1997-03-03 16:03:27 +00:00
|
|
|
\begin{funcdesc}{intern}{string}
|
|
|
|
Enter \var{string} in the table of ``interned'' strings and return
|
|
|
|
the interned string -- which is \var{string} itself or a copy.
|
|
|
|
Interning strings is useful to gain a little performance on
|
|
|
|
dictionary lookup -- if the keys in a dictionary are interned, and
|
|
|
|
the lookup key is interned, the key comparisons (after hashing) can
|
|
|
|
be done by a pointer compare instead of a string compare. Normally,
|
|
|
|
the names used in Python programs are automatically interned, and
|
|
|
|
the dictionaries used to hold module, class or instance attributes
|
|
|
|
have interned keys. Interned strings are immortal (i.e. never get
|
|
|
|
garbage collected).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\begin{funcdesc}{int}{x}
|
1997-04-02 06:04:02 +00:00
|
|
|
Convert a string or number to a plain integer. If the argument is a
|
|
|
|
string, it must contain a possibly singed decimal number
|
|
|
|
representable as a Python integer, possibly embedded in whitespace;
|
|
|
|
this behaves identical to \code{string.atoi(\var{x})}.
|
|
|
|
Otherwise, the argument may be a plain or
|
1995-03-17 16:07:09 +00:00
|
|
|
long integer or a floating point number. Conversion of floating
|
|
|
|
point numbers to integers is defined by the C semantics; normally
|
1995-03-28 13:35:14 +00:00
|
|
|
the conversion truncates towards zero.\footnote{This is ugly --- the
|
|
|
|
language definition should require truncation towards zero.}
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1997-10-05 18:53:00 +00:00
|
|
|
\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.
|
1997-12-02 19:15:01 +00:00
|
|
|
Also return true if \var{class} is a type object and \var{object} is
|
|
|
|
an object of that type. If \var{object} is not a class instance or a
|
|
|
|
object of the given type, the function always returns false. If
|
|
|
|
\var{class} is neither a class object nor a type object, a
|
1998-03-03 21:56:15 +00:00
|
|
|
\exception{TypeError} exception is raised.
|
1997-10-05 18:53:00 +00:00
|
|
|
\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
|
1998-03-03 21:56:15 +00:00
|
|
|
argument is not a class object, a \exception{TypeError} exception is
|
|
|
|
raised.
|
1997-10-05 18:53:00 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\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).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1997-06-02 17:21:20 +00:00
|
|
|
\begin{funcdesc}{list}{sequence}
|
|
|
|
Return a list whose items are the same and in the same order as
|
|
|
|
\var{sequence}'s items. If \var{sequence} is already a list,
|
|
|
|
a copy is made and returned, similar to \code{\var{sequence}[:]}.
|
|
|
|
For instance, \code{list('abc')} returns
|
|
|
|
returns \code{['a', 'b', 'c']} and \code{list( (1, 2, 3) )} returns
|
|
|
|
\code{[1, 2, 3]}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1995-07-07 22:58:28 +00:00
|
|
|
\begin{funcdesc}{locals}{}
|
|
|
|
Return a dictionary representing the current local symbol table.
|
1998-06-18 16:45:34 +00:00
|
|
|
\strong{Warning:} the contents of this dictionary should not be
|
|
|
|
modified; changes may not affect the values of local variables used by
|
|
|
|
the interpreter.
|
1995-07-07 22:58:28 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\begin{funcdesc}{long}{x}
|
1997-04-02 06:04:02 +00:00
|
|
|
Convert a string or number to a long integer. If the argument is a
|
|
|
|
string, it must contain a possibly singed decimal number of
|
|
|
|
arbitrary size, possibly embedded in whitespace;
|
|
|
|
this behaves identical to \code{string.atol(\var{x})}.
|
|
|
|
Otherwise, the argument may be a plain or
|
1997-12-30 20:38:16 +00:00
|
|
|
long integer or a floating point number, and a long integer with
|
1997-04-02 06:04:02 +00:00
|
|
|
the same value is returned. Conversion of floating
|
|
|
|
point numbers to integers is defined by the C semantics;
|
1998-03-03 21:56:15 +00:00
|
|
|
see the description of \function{int()}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{map}{function, list, ...}
|
1994-01-02 01:22:07 +00:00
|
|
|
Apply \var{function} to every item of \var{list} and return a list
|
|
|
|
of the results. If additional \var{list} arguments are passed,
|
|
|
|
\var{function} must take that many arguments and is applied to
|
|
|
|
the items of all lists in parallel; if a list is shorter than another
|
|
|
|
it is assumed to be extended with \code{None} items. If
|
|
|
|
\var{function} is \code{None}, the identity function is assumed; if
|
1998-03-03 21:56:15 +00:00
|
|
|
there are multiple list arguments, \function{map()} returns a list
|
1994-01-02 01:22:07 +00:00
|
|
|
consisting of tuples containing the corresponding items from all lists
|
|
|
|
(i.e. a kind of transpose operation). The \var{list} arguments may be
|
|
|
|
any kind of sequence; the result is always a list.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{max}{s}
|
|
|
|
Return the largest item of a non-empty sequence (string, tuple or
|
|
|
|
list).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{min}{s}
|
|
|
|
Return the smallest item of a non-empty sequence (string, tuple or
|
|
|
|
list).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{oct}{x}
|
1995-03-17 16:07:09 +00:00
|
|
|
Convert an integer number (of any size) to an octal string. The
|
1997-01-14 18:44:23 +00:00
|
|
|
result is a valid Python expression. Note: this always yields
|
|
|
|
an unsigned literal, e.g. on a 32-bit machine, \code{oct(-1)} yields
|
|
|
|
\code{'037777777777'}. When evaluated on a machine with the same
|
|
|
|
word size, this literal is evaluated as -1; at a different word
|
|
|
|
size, it may turn up as a large positive number or raise an
|
1998-03-03 21:56:15 +00:00
|
|
|
\exception{OverflowError} exception.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{open}{filename\optional{, mode\optional{, bufsize}}}
|
1994-01-02 01:22:07 +00:00
|
|
|
Return a new file object (described earlier under Built-in Types).
|
1994-05-03 14:46:50 +00:00
|
|
|
The first two arguments are the same as for \code{stdio}'s
|
1998-03-03 21:56:15 +00:00
|
|
|
\cfunction{fopen()}: \var{filename} is the file name to be opened,
|
1994-01-02 01:22:07 +00:00
|
|
|
\var{mode} indicates how the file is to be opened: \code{'r'} for
|
|
|
|
reading, \code{'w'} for writing (truncating an existing file), and
|
1998-01-14 14:51:31 +00:00
|
|
|
\code{'a'} opens it for appending (which on \emph{some} \UNIX{}
|
|
|
|
systems means that \emph{all} writes append to the end of the file,
|
1996-05-02 15:16:59 +00:00
|
|
|
regardless of the current seek position).
|
1998-07-29 21:05:35 +00:00
|
|
|
|
|
|
|
Modes \code{'r+'}, \code{'w+'} and \code{'a+'} open the file for
|
|
|
|
updating (note that \code{'w+'} truncates the file). Append
|
|
|
|
\code{'b'} to the mode to open the file in binary mode, on systems
|
|
|
|
that differentiate between binary and text files (else it is
|
|
|
|
ignored). If the file cannot be opened, \exception{IOError} is
|
|
|
|
raised.
|
|
|
|
|
1994-05-03 14:46:50 +00:00
|
|
|
If \var{mode} is omitted, it defaults to \code{'r'}.
|
|
|
|
The optional \var{bufsize} argument specifies the file's desired
|
|
|
|
buffer size: 0 means unbuffered, 1 means line buffered, any other
|
|
|
|
positive value means use a buffer of (approximately) that size. A
|
|
|
|
negative \var{bufsize} means to use the system default, which is
|
|
|
|
usually line buffered for for tty devices and fully buffered for other
|
|
|
|
files.%
|
|
|
|
\footnote{Specifying a buffer size currently has no effect on systems
|
1998-03-03 21:56:15 +00:00
|
|
|
that don't have \cfunction{setvbuf()}. The interface to specify the buffer
|
|
|
|
size is not done using a method that calls \cfunction{setvbuf()}, because
|
1994-05-03 14:46:50 +00:00
|
|
|
that may dump core when called after any I/O has been performed, and
|
|
|
|
there's no reliable way to determine whether this is the case.}
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{ord}{c}
|
|
|
|
Return the \ASCII{} value of a string of one character. E.g.,
|
|
|
|
\code{ord('a')} returns the integer \code{97}. This is the inverse of
|
1998-03-03 21:56:15 +00:00
|
|
|
\function{chr()}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{pow}{x, y\optional{, z}}
|
1994-08-12 13:13:50 +00:00
|
|
|
Return \var{x} to the power \var{y}; if \var{z} is present, return
|
|
|
|
\var{x} to the power \var{y}, modulo \var{z} (computed more
|
1998-04-03 07:15:54 +00:00
|
|
|
efficiently than \code{pow(\var{x}, \var{y}) \%\ \var{z}}).
|
1994-08-12 13:13:50 +00:00
|
|
|
The arguments must have
|
1994-01-02 01:22:07 +00:00
|
|
|
numeric types. With mixed operand types, the rules for binary
|
|
|
|
arithmetic operators apply. The effective operand type is also the
|
|
|
|
type of the result; if the result is not expressible in this type, the
|
1994-08-08 12:30:22 +00:00
|
|
|
function raises an exception; e.g., \code{pow(2, -1)} or \code{pow(2,
|
|
|
|
35000)} is not allowed.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{range}{\optional{start,} stop\optional{, step}}
|
1994-01-02 01:22:07 +00:00
|
|
|
This is a versatile function to create lists containing arithmetic
|
1998-03-03 21:56:15 +00:00
|
|
|
progressions. It is most often used in \keyword{for} loops. The
|
1994-01-02 01:22:07 +00:00
|
|
|
arguments must be plain integers. If the \var{step} argument is
|
|
|
|
omitted, it defaults to \code{1}. If the \var{start} argument is
|
|
|
|
omitted, it defaults to \code{0}. The full form returns a list of
|
|
|
|
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} *
|
1997-10-05 18:53:00 +00:00
|
|
|
\var{step}} less than \var{stop}; if \var{step} is negative, the last
|
1994-01-02 01:22:07 +00:00
|
|
|
element is the largest \code{\var{start} + \var{i} * \var{step}}
|
1998-04-03 07:15:54 +00:00
|
|
|
greater than \var{stop}. \var{step} must not be zero (or else
|
|
|
|
\exception{ValueError} is raised). Example:
|
1994-01-02 01:22:07 +00:00
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\begin{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
>>> range(10)
|
|
|
|
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
|
|
|
|
>>> range(1, 11)
|
|
|
|
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
|
|
|
|
>>> range(0, 30, 5)
|
|
|
|
[0, 5, 10, 15, 20, 25]
|
|
|
|
>>> range(0, 10, 3)
|
|
|
|
[0, 3, 6, 9]
|
|
|
|
>>> range(0, -10, -1)
|
|
|
|
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
|
|
|
|
>>> range(0)
|
|
|
|
[]
|
|
|
|
>>> range(1, 0)
|
|
|
|
[]
|
|
|
|
>>>
|
1998-02-13 06:58:54 +00:00
|
|
|
\end{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-08-08 12:30:22 +00:00
|
|
|
\begin{funcdesc}{raw_input}{\optional{prompt}}
|
|
|
|
If the \var{prompt} argument is present, it is written to standard output
|
|
|
|
without a trailing newline. The function then reads a line from input,
|
|
|
|
converts it to a string (stripping a trailing newline), and returns that.
|
1998-03-03 21:56:15 +00:00
|
|
|
When \EOF{} is read, \exception{EOFError} is raised. Example:
|
1994-01-02 01:22:07 +00:00
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\begin{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
>>> s = raw_input('--> ')
|
|
|
|
--> Monty Python's Flying Circus
|
|
|
|
>>> s
|
1995-03-17 16:07:09 +00:00
|
|
|
"Monty Python's Flying Circus"
|
1994-01-02 01:22:07 +00:00
|
|
|
>>>
|
1998-02-13 06:58:54 +00:00
|
|
|
\end{verbatim}
|
1997-06-02 17:21:20 +00:00
|
|
|
|
1998-03-03 21:56:15 +00:00
|
|
|
If the \module{readline} module was loaded, then
|
|
|
|
\function{raw_input()} will use it to provide elaborate
|
1997-06-02 17:21:20 +00:00
|
|
|
line editing and history features.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{reduce}{function, list\optional{, initializer}}
|
1994-01-02 01:22:07 +00:00
|
|
|
Apply the binary \var{function} to the items of \var{list} so as to
|
|
|
|
reduce the list to a single value. E.g.,
|
|
|
|
\code{reduce(lambda x, y: x*y, \var{list}, 1)} returns the product of
|
|
|
|
the elements of \var{list}. The optional \var{initializer} can be
|
|
|
|
thought of as being prepended to \var{list} so as to allow reduction
|
|
|
|
of an empty \var{list}. The \var{list} arguments may be any kind of
|
|
|
|
sequence.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{reload}{module}
|
1995-03-17 16:07:09 +00:00
|
|
|
Re-parse and re-initialize an already imported \var{module}. The
|
|
|
|
argument must be a module object, so it must have been successfully
|
|
|
|
imported before. This is useful if you have edited the module source
|
|
|
|
file using an external editor and want to try out the new version
|
|
|
|
without leaving the Python interpreter. The return value is the
|
|
|
|
module object (i.e.\ the same as the \var{module} argument).
|
|
|
|
|
|
|
|
There are a number of caveats:
|
|
|
|
|
|
|
|
If a module is syntactically correct but its initialization fails, the
|
1998-03-03 21:56:15 +00:00
|
|
|
first \keyword{import} statement for it does not bind its name locally,
|
1995-03-17 16:07:09 +00:00
|
|
|
but does store a (partially initialized) module object in
|
|
|
|
\code{sys.modules}. To reload the module you must first
|
1998-03-03 21:56:15 +00:00
|
|
|
\keyword{import} it again (this will bind the name to the partially
|
|
|
|
initialized module object) before you can \function{reload()} it.
|
1995-03-17 16:07:09 +00:00
|
|
|
|
|
|
|
When a module is reloaded, its dictionary (containing the module's
|
|
|
|
global variables) is retained. Redefinitions of names will override
|
|
|
|
the old definitions, so this is generally not a problem. If the new
|
|
|
|
version of a module does not define a name that was defined by the old
|
|
|
|
version, the old definition remains. This feature can be used to the
|
|
|
|
module's advantage if it maintains a global table or cache of objects
|
1998-03-03 21:56:15 +00:00
|
|
|
--- with a \keyword{try} statement it can test for the table's presence
|
1995-03-17 16:07:09 +00:00
|
|
|
and skip its initialization if desired.
|
|
|
|
|
|
|
|
It is legal though generally not very useful to reload built-in or
|
1998-03-03 21:56:15 +00:00
|
|
|
dynamically loaded modules, except for \module{sys}, \module{__main__}
|
|
|
|
and \module{__builtin__}. In certain cases, however, extension
|
|
|
|
modules are not designed to be initialized more than once, and may
|
|
|
|
fail in arbitrary ways when reloaded.
|
|
|
|
|
|
|
|
If a module imports objects from another module using \keyword{from}
|
|
|
|
\ldots{} \keyword{import} \ldots{}, calling \function{reload()} for
|
|
|
|
the other module does not redefine the objects imported from it ---
|
|
|
|
one way around this is to re-execute the \keyword{from} statement,
|
|
|
|
another is to use \keyword{import} and qualified names
|
|
|
|
(\var{module}.\var{name}) instead.
|
1995-03-17 16:07:09 +00:00
|
|
|
|
|
|
|
If a module instantiates instances of a class, reloading the module
|
|
|
|
that defines the class does not affect the method definitions of the
|
|
|
|
instances --- they continue to use the old class definition. The same
|
|
|
|
is true for derived classes.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
|
|
|
\begin{funcdesc}{repr}{object}
|
|
|
|
Return a string containing a printable representation of an object.
|
|
|
|
This is the same value yielded by conversions (reverse quotes).
|
|
|
|
It is sometimes useful to be able to access this operation as an
|
|
|
|
ordinary function. For many types, this function makes an attempt
|
|
|
|
to return a string that would yield an object with the same value
|
1998-03-03 21:56:15 +00:00
|
|
|
when passed to \function{eval()}.
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{round}{x, n}
|
1994-01-02 01:22:07 +00:00
|
|
|
Return the floating point value \var{x} rounded to \var{n} digits
|
|
|
|
after the decimal point. If \var{n} is omitted, it defaults to zero.
|
|
|
|
The result is a floating point number. Values are rounded to the
|
|
|
|
closest multiple of 10 to the power minus \var{n}; if two multiples
|
|
|
|
are equally close, rounding is done away from 0 (so e.g.
|
|
|
|
\code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}).
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{setattr}{object, name, value}
|
1998-03-03 21:56:15 +00:00
|
|
|
This is the counterpart of \function{getattr()}. The arguments are an
|
1994-01-02 01:22:07 +00:00
|
|
|
object, a string and an arbitrary value. The string must be the name
|
|
|
|
of one of the object's attributes. The function assigns the value to
|
|
|
|
the attribute, provided the object allows it. For example,
|
|
|
|
\code{setattr(\var{x}, '\var{foobar}', 123)} is equivalent to
|
|
|
|
\code{\var{x}.\var{foobar} = 123}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{slice}{\optional{start,} stop\optional{, step}}
|
1997-10-05 18:53:00 +00:00
|
|
|
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
|
1998-03-03 21:56:15 +00:00
|
|
|
read-only data attributes \member{start}, \member{stop} and \member{step}
|
1997-10-05 18:53:00 +00:00
|
|
|
which merely return the argument values (or their default). They have
|
|
|
|
no other explicit functionality; however they are used by Numerical
|
1998-04-03 07:15:54 +00:00
|
|
|
Python\index{Numerical Python} and other third party extensions.
|
|
|
|
Slice objects are also generated when extended indexing syntax is
|
|
|
|
used, e.g. for \samp{a[start:stop:step]} or \samp{a[start:stop, i]}.
|
1997-10-05 18:53:00 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\begin{funcdesc}{str}{object}
|
|
|
|
Return a string containing a nicely printable representation of an
|
|
|
|
object. For strings, this returns the string itself. The difference
|
1995-03-07 10:14:09 +00:00
|
|
|
with \code{repr(\var{object})} is that \code{str(\var{object})} does not
|
1998-03-03 21:56:15 +00:00
|
|
|
always attempt to return a string that is acceptable to \function{eval()};
|
1994-01-02 01:22:07 +00:00
|
|
|
its goal is to return a printable string.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1995-03-17 16:07:09 +00:00
|
|
|
\begin{funcdesc}{tuple}{sequence}
|
1994-08-12 13:13:50 +00:00
|
|
|
Return a tuple whose items are the same and in the same order as
|
1997-06-02 17:21:20 +00:00
|
|
|
\var{sequence}'s items. If \var{sequence} is already a tuple, it
|
1994-08-12 13:13:50 +00:00
|
|
|
is returned unchanged. For instance, \code{tuple('abc')} returns
|
|
|
|
returns \code{('a', 'b', 'c')} and \code{tuple([1, 2, 3])} returns
|
|
|
|
\code{(1, 2, 3)}.
|
|
|
|
\end{funcdesc}
|
|
|
|
|
1994-01-02 01:22:07 +00:00
|
|
|
\begin{funcdesc}{type}{object}
|
1995-03-17 16:07:09 +00:00
|
|
|
Return the type of an \var{object}. The return value is a type
|
1998-03-03 21:56:15 +00:00
|
|
|
object. The standard module \module{types} defines names for all
|
1995-03-17 16:07:09 +00:00
|
|
|
built-in types.
|
1997-12-15 22:28:38 +00:00
|
|
|
\refstmodindex{types}
|
1995-03-17 16:07:09 +00:00
|
|
|
\obindex{type}
|
|
|
|
For instance:
|
1994-01-02 01:22:07 +00:00
|
|
|
|
1998-02-13 06:58:54 +00:00
|
|
|
\begin{verbatim}
|
1995-03-17 16:07:09 +00:00
|
|
|
>>> import types
|
1998-06-22 14:07:36 +00:00
|
|
|
>>> if type(x) == types.StringType: print "It's a string"
|
1998-02-13 06:58:54 +00:00
|
|
|
\end{verbatim}
|
1994-01-02 01:22:07 +00:00
|
|
|
\end{funcdesc}
|
1994-02-24 11:28:27 +00:00
|
|
|
|
1995-03-13 10:03:32 +00:00
|
|
|
\begin{funcdesc}{vars}{\optional{object}}
|
1994-04-21 10:32:28 +00:00
|
|
|
Without arguments, return a dictionary corresponding to the current
|
|
|
|
local symbol table. With a module, class or class instance object as
|
1998-03-03 21:56:15 +00:00
|
|
|
argument (or anything else that has a \member{__dict__} attribute),
|
1994-04-21 10:32:28 +00:00
|
|
|
returns a dictionary corresponding to the object's symbol table.
|
|
|
|
The returned dictionary should not be modified: the effects on the
|
|
|
|
corresponding symbol table are undefined.%
|
|
|
|
\footnote{In the current implementation, local variable bindings
|
|
|
|
cannot normally be affected this way, but variables retrieved from
|
1995-03-07 10:14:09 +00:00
|
|
|
other scopes (e.g. modules) can be. This may change.}
|
1994-04-21 10:32:28 +00:00
|
|
|
\end{funcdesc}
|
|
|
|
|
1998-03-17 06:33:25 +00:00
|
|
|
\begin{funcdesc}{xrange}{\optional{start,} stop\optional{, step}}
|
1998-03-03 21:56:15 +00:00
|
|
|
This function is very similar to \function{range()}, but returns an
|
1994-02-24 11:28:27 +00:00
|
|
|
``xrange object'' instead of a list. This is an opaque sequence type
|
|
|
|
which yields the same values as the corresponding list, without
|
|
|
|
actually storing them all simultaneously. The advantage of
|
1998-03-03 21:56:15 +00:00
|
|
|
\function{xrange()} over \function{range()} is minimal (since
|
|
|
|
\function{xrange()} still has to create the values when asked for
|
|
|
|
them) except when a very large range is used on a memory-starved
|
|
|
|
machine (e.g. MS-DOS) or when all of the range's elements are never
|
|
|
|
used (e.g. when the loop is usually terminated with \keyword{break}).
|
1994-02-24 11:28:27 +00:00
|
|
|
\end{funcdesc}
|