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      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 
     10 from _functools import partial, reduce
     11 
     12 # update_wrapper() and wraps() are tools to help write
     13 # wrapper functions that can handle naive introspection
     14 
     15 WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__')
     16 WRAPPER_UPDATES = ('__dict__',)
     17 def 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 
     39 def 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 
     53 def 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 
     80 def 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