When defining a decorator using a class, how do I automatically transfer over__name__, __module__ and __doc__? Normally, I would use the @wraps decorator from functools. Here's what I did instead for a class (this is not entirely my code):
class memoized:
"""Decorator that caches a function's return value each time it is called.
If called later with the same arguments, the cached value is returned, and
not re-evaluated.
"""
def __init__(self, func):
super().__init__()
self.func = func
self.cache = {}
def __call__(self, *args):
try:
return self.cache[args]
except KeyError:
value = self.func(*args)
self.cache[args] = value
return value
except TypeError:
# uncacheable -- for instance, passing a list as an argument.
# Better to not cache than to blow up entirely.
return self.func(*args)
def __repr__(self):
return self.func.__repr__()
def __get__(self, obj, objtype):
return functools.partial(self.__call__, obj)
__doc__ = property(lambda self:self.func.__doc__)
__module__ = property(lambda self:self.func.__module__)
__name__ = property(lambda self:self.func.__name__)
Is there a standard decorator to automate the creation of name module and doc? Also, to automate the get method (I assume that's for creating bound methods?) Are there any missing methods?
Everyone seems to have missed the obvious solution. Using functools.update_wrapper:
>>> import functools
>>> class memoized(object):
"""Decorator that caches a function's return value each time it is called.
If called later with the same arguments, the cached value is returned, and
not re-evaluated.
"""
def __init__(self, func):
self.func = func
self.cache = {}
functools.update_wrapper(self, func) ## TA-DA! ##
def __call__(self, *args):
pass # Not needed for this demo.
>>> @memoized
def fibonacci(n):
"""fibonacci docstring"""
pass # Not needed for this demo.
>>> fibonacci
<__main__.memoized object at 0x0156DE30>
>>> fibonacci.__name__
'fibonacci'
>>> fibonacci.__doc__
'fibonacci docstring'