Aluode/PerceptionLabPortable

1import types2import functools3 4 5# from jaraco.functools 3.36def method_cache(method, cache_wrapper=None):7    """8    Wrap lru_cache to support storing the cache data in the object instances.9 10    Abstracts the common paradigm where the method explicitly saves an11    underscore-prefixed protected property on first call and returns that12    subsequently.13 14    >>> class MyClass:15    ...     calls = 016    ...17    ...     @method_cache18    ...     def method(self, value):19    ...         self.calls += 120    ...         return value21 22    >>> a = MyClass()23    >>> a.method(3)24    325    >>> for x in range(75):26    ...     res = a.method(x)27    >>> a.calls28    7529 30    Note that the apparent behavior will be exactly like that of lru_cache31    except that the cache is stored on each instance, so values in one32    instance will not flush values from another, and when an instance is33    deleted, so are the cached values for that instance.34 35    >>> b = MyClass()36    >>> for x in range(35):37    ...     res = b.method(x)38    >>> b.calls39    3540    >>> a.method(0)41    042    >>> a.calls43    7544 45    Note that if method had been decorated with ``functools.lru_cache()``,46    a.calls would have been 76 (due to the cached value of 0 having been47    flushed by the 'b' instance).48 49    Clear the cache with ``.cache_clear()``50 51    >>> a.method.cache_clear()52 53    Same for a method that hasn't yet been called.54 55    >>> c = MyClass()56    >>> c.method.cache_clear()57 58    Another cache wrapper may be supplied:59 60    >>> cache = functools.lru_cache(maxsize=2)61    >>> MyClass.method2 = method_cache(lambda self: 3, cache_wrapper=cache)62    >>> a = MyClass()63    >>> a.method2()64    365 66    Caution - do not subsequently wrap the method with another decorator, such67    as ``@property``, which changes the semantics of the function.68 69    See also70    http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/71    for another implementation and additional justification.72    """73    cache_wrapper = cache_wrapper or functools.lru_cache()74 75    def wrapper(self, *args, **kwargs):76        # it's the first call, replace the method with a cached, bound method77        bound_method = types.MethodType(method, self)78        cached_method = cache_wrapper(bound_method)79        setattr(self, method.__name__, cached_method)80        return cached_method(*args, **kwargs)81 82    # Support cache clear even before cache has been created.83    wrapper.cache_clear = lambda: None84 85    return wrapper86 87 88# From jaraco.functools 3.389def pass_none(func):90    """91    Wrap func so it's not called if its first param is None92 93    >>> print_text = pass_none(print)94    >>> print_text('text')95    text96    >>> print_text(None)97    """98 99    @functools.wraps(func)100    def wrapper(param, *args, **kwargs):101        if param is not None:102            return func(param, *args, **kwargs)103 104    return wrapper105