How short & how complete can we write a memoising decorator? I think the below is more complete than most formulations (which don't cache independent of arg-binding.) I think it also cuts straight to the core of what memoisation means. Three obvious deficiencies: [1] What do we do about instance and class methods? These can be meaningfully memoi…

memoise.py

from sys import version_info
assert version_info.major == 3 and version_info.minor >= 3, \
  'requires PEP 362; Python 3.3 or later; python.org/dev/peps/pep-0362/'

from inspect import signature
class memoise(dict):
	def __init__(self, func):
		self.func, self.signature = func, signature(func)
	def __missing__(self, key):
		args, kwargs = key
		self[key] = self.func(*args, **dict(kwargs))
		return self[key]
	def __call__(self, *args, **kwargs):
		key = self.signature.bind(*args, **kwargs)
		return self[key.args, frozenset(key.kwargs.items())]
		
class Foo(object):
	@memoise
	def bar(x, y, z):
		print('Foo.bar({}, {}, {})'.format(x, y, z))
		return x + y + z

if __name__ == '__main__':
	f = Foo()
	assert f.foo(1,2,3) == f.bar(z=3,y=2,x=1)