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
  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: other < self),
  57                    ('__le__', lambda self, other: not other < self),
  58                    ('__ge__', lambda self, other: not self < other)],
  59         '__le__': [('__ge__', lambda self, other: other <= self),
  60                    ('__lt__', lambda self, other: not other <= self),
  61                    ('__gt__', lambda self, other: not self <= other)],
  62         '__gt__': [('__lt__', lambda self, other: other > self),
  63                    ('__ge__', lambda self, other: not other > self),
  64                    ('__le__', lambda self, other: not self > other)],
  65         '__ge__': [('__le__', lambda self, other: other >= self),
  66                    ('__gt__', lambda self, other: not other >= self),
  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         def __init__(self, obj, *args):
  84             self.obj = obj
  85         def __lt__(self, other):
  86             return mycmp(self.obj, other.obj) < 0
  87         def __gt__(self, other):
  88             return mycmp(self.obj, other.obj) > 0
  89         def __eq__(self, other):
  90             return mycmp(self.obj, other.obj) == 0
  91         def __le__(self, other):
  92             return mycmp(self.obj, other.obj) <= 0
  93         def __ge__(self, other):
  94             return mycmp(self.obj, other.obj) >= 0
  95         def __ne__(self, other):
  96             return mycmp(self.obj, other.obj) != 0
  97         def __hash__(self):
  98             raise TypeError('hash not implemented')
  99     return K