src/third_party/blink/Tools/Scripts/webkitpy/common/memoized.py

# Copyright (c) 2010 Google Inc. All rights reserved.
#
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# Python does not (yet) seem to provide automatic memoization.  So we've
# written a small decorator to do so.

import functools


class memoized(object):

    def __init__(self, function):
        self._function = function
        self._results_cache = {}

    def __call__(self, *args):
        try:
            return self._results_cache[args]
        except KeyError:
            result = self._function(*args)
            self._results_cache[args] = result
            return result
        except TypeError as error:
            raise TypeError(
                'Cannot call memoized function %s with unhashable '
                'arguments: %s' % (self._function.__name__, error.message))

    # Use python "descriptor" protocol __get__ to appear
    # invisible during property access.
    def __get__(self, instance, owner):
        # Return a function partial with object already bound as self.
        return functools.partial(self.__call__, instance)