/Lib/functools.py

 1"""functools.py - Tools for working with functions and callable objects
 2"""
 3# Python module wrapper for _functools C module
 4# to allow utilities written in Python to be added
 5# to the functools module.
 6# Written by Nick Coghlan <ncoghlan at gmail.com>
 7#   Copyright (C) 2006 Python Software Foundation.
 8# See C source code for _functools credits/copyright
 9
10from _functools import partial, reduce
11
12# update_wrapper() and wraps() are tools to help write
13# wrapper functions that can handle naive introspection
14
15WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__')
16WRAPPER_UPDATES = ('__dict__',)
17def update_wrapper(wrapper,
18                   wrapped,
19                   assigned = WRAPPER_ASSIGNMENTS,
20                   updated = WRAPPER_UPDATES):
21    """Update a wrapper function to look like the wrapped function
22
23       wrapper is the function to be updated
24       wrapped is the original function
25       assigned is a tuple naming the attributes assigned directly
26       from the wrapped function to the wrapper function (defaults to
27       functools.WRAPPER_ASSIGNMENTS)
28       updated is a tuple naming the attributes of the wrapper that
29       are updated with the corresponding attribute from the wrapped
30       function (defaults to functools.WRAPPER_UPDATES)
31    """
32    for attr in assigned:
33        setattr(wrapper, attr, getattr(wrapped, attr))
34    for attr in updated:
35        getattr(wrapper, attr).update(getattr(wrapped, attr, {}))
36    # Return the wrapper so this can be used as a decorator via partial()
37    return wrapper
38
39def wraps(wrapped,
40          assigned = WRAPPER_ASSIGNMENTS,
41          updated = WRAPPER_UPDATES):
42    """Decorator factory to apply update_wrapper() to a wrapper function
43
44       Returns a decorator that invokes update_wrapper() with the decorated
45       function as the wrapper argument and the arguments to wraps() as the
46       remaining arguments. Default arguments are as for update_wrapper().
47       This is a convenience function to simplify applying partial() to
48       update_wrapper().
49    """
50    return partial(update_wrapper, wrapped=wrapped,
51                   assigned=assigned, updated=updated)