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)
52
53def total_ordering(cls):
54    """Class decorator that fills in missing ordering methods"""
55    convert = {
56        '__lt__': [('__gt__', lambda self, other: not (self < other or self == other)),
57                   ('__le__', lambda self, other: self < other or self == other),
58                   ('__ge__', lambda self, other: not self < other)],
59        '__le__': [('__ge__', lambda self, other: not self <= other or self == other),
60                   ('__lt__', lambda self, other: self <= other and not self == other),
61                   ('__gt__', lambda self, other: not self <= other)],
62        '__gt__': [('__lt__', lambda self, other: not (self > other or self == other)),
63                   ('__ge__', lambda self, other: self > other or self == other),
64                   ('__le__', lambda self, other: not self > other)],
65        '__ge__': [('__le__', lambda self, other: (not self >= other) or self == other),
66                   ('__gt__', lambda self, other: self >= other and not self == other),
67                   ('__lt__', lambda self, other: not self >= other)]
68    }
69    roots = set(dir(cls)) & set(convert)
70    if not roots:
71        raise ValueError('must define at least one ordering operation: < > <= >=')
72    root = max(roots)       # prefer __lt__ to __le__ to __gt__ to __ge__
73    for opname, opfunc in convert[root]:
74        if opname not in roots:
75            opfunc.__name__ = opname
76            opfunc.__doc__ = getattr(int, opname).__doc__
77            setattr(cls, opname, opfunc)
78    return cls
79
80def cmp_to_key(mycmp):
81    """Convert a cmp= function into a key= function"""
82    class K(object):
83        __slots__ = ['obj']
84        def __init__(self, obj, *args):
85            self.obj = obj
86        def __lt__(self, other):
87            return mycmp(self.obj, other.obj) < 0
88        def __gt__(self, other):
89            return mycmp(self.obj, other.obj) > 0
90        def __eq__(self, other):
91            return mycmp(self.obj, other.obj) == 0
92        def __le__(self, other):
93            return mycmp(self.obj, other.obj) <= 0
94        def __ge__(self, other):
95            return mycmp(self.obj, other.obj) >= 0
96        def __ne__(self, other):
97            return mycmp(self.obj, other.obj) != 0
98        def __hash__(self):
99            raise TypeError('hash not implemented')
100    return K
101