New in version 2.5.
The functools module is for higher-order functions: functions
that act on or return other functions. In general, any callable object can
be treated as a function for the purposes of this module.
The functools module defines the following function:
partial( |
func[,*args][, **keywords]) |
-
Return a new partial object which when called will behave like
func called with the positional arguments args and keyword
arguments keywords. If more arguments are supplied to the call, they
are appended to args. If additional keyword arguments are supplied,
they extend and override keywords. Roughly equivalent to:
def partial(func, *args, **keywords):
def newfunc(*fargs, **fkeywords):
newkeywords = keywords.copy()
newkeywords.update(fkeywords)
return func(*(args + fargs), **newkeywords)
newfunc.func = func
newfunc.args = args
newfunc.keywords = keywords
return newfunc
The partial is used for partial function application which
``freezes'' some portion of a function's arguments and/or keywords
resulting in a new object with a simplified signature. For example,
partial can be used to create a callable that behaves like
the int function where the base argument defaults to
two:
>>> basetwo = partial(int, base=2)
>>> basetwo.__doc__ = 'Convert base 2 string to an int.'
>>> basetwo('10010')
18
update_wrapper( |
wrapper, wrapped[, assigned][, updated]) |
-
Update a wrapper function to look like the wrapped function.
The optional arguments are tuples to specify which attributes of the original
function are assigned directly to the matching attributes on the wrapper
function and which attributes of the wrapper function are updated with
the corresponding attributes from the original function. The default
values for these arguments are the module level constants
WRAPPER_ASSIGNMENTS (which assigns to the wrapper function's
__name__, __module__ and __doc__, the documentation string)
and WRAPPER_UPDATES (which updates the wrapper function's __dict__,
i.e. the instance dictionary).
The main intended use for this function is in decorator functions
which wrap the decorated function and return the wrapper. If the
wrapper function is not updated, the metadata of the returned function
will reflect the wrapper definition rather than the original function
definition, which is typically less than helpful.
wraps( |
wrapped[, assigned][, updated]) |
-
This is a convenience function for invoking
partial(update_wrapper, wrapped=wrapped, assigned=assigned, updated=updated)
as a function decorator when defining a wrapper function. For example:
>>> def my_decorator(f):
... @wraps(f)
... def wrapper(*args, **kwds):
... print 'Calling decorated function'
... return f(*args, **kwds)
... return wrapper
...
>>> @my_decorator
... def example():
... """Docstring"""
... print 'Called example function'
...
>>> example()
Calling decorated function
Called example function
>>> example.__name__
'example'
>>> example.__doc__
'Docstring'
Without the use of this decorator factory, the name of the example
function would have been 'wrapper' , and the docstring of the
original example() would have been lost.
Release 2.5.2, documentation updated on 21st February, 2008.
See About this document... for information on suggesting changes.
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