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
  11 from __builtin__ import reduce
  12
  13 # update_wrapper() and wraps() are tools to help write
  14 # wrapper functions that can handle naive introspection
  15
  16 WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__')
  17 WRAPPER_UPDATES = ('__dict__',)
  18 def update_wrapper(wrapper,
  19                    wrapped,
  20                    assigned = WRAPPER_ASSIGNMENTS,
  21                    updated = WRAPPER_UPDATES):
  22     """Update a wrapper function to look like the wrapped function
  23
  24        wrapper is the function to be updated
  25        wrapped is the original function
  26        assigned is a tuple naming the attributes assigned directly
  27        from the wrapped function to the wrapper function (defaults to
  28        functools.WRAPPER_ASSIGNMENTS)
  29        updated is a tuple naming the attributes of the wrapper that
  30        are updated with the corresponding attribute from the wrapped
  31        function (defaults to functools.WRAPPER_UPDATES)
  32     """
  33     for attr in assigned:
  34         setattr(wrapper, attr, getattr(wrapped, attr))
  35     for attr in updated:
  36         getattr(wrapper, attr).update(getattr(wrapped, attr, {}))
  37     # Return the wrapper so this can be used as a decorator via partial()
  38     return wrapper
  39
  40 def wraps(wrapped,
  41           assigned = WRAPPER_ASSIGNMENTS,
  42           updated = WRAPPER_UPDATES):
  43     """Decorator factory to apply update_wrapper() to a wrapper function
  44
  45        Returns a decorator that invokes update_wrapper() with the decorated
  46        function as the wrapper argument and the arguments to wraps() as the
  47        remaining arguments. Default arguments are as for update_wrapper().
  48        This is a convenience function to simplify applying partial() to
  49        update_wrapper().
  50     """
  51     return partial(update_wrapper, wrapped=wrapped,
  52                    assigned=assigned, updated=updated)