Memoizing decorator, caches function's return value, expires after ttl time in seconds or ctl calls - Python

memoized.py

import time

class memoized(object):
    def __init__(self, ctl=3, ttl=2):
        self.cache = {}
        self.ctl = ctl
        self.ttl = ttl
        self._call_count = 1

    def __call__(self, func):
        def _memoized(*args):
            self.func = func
            now = time.time()
            try:
                value, last_update = self.cache[args]
                age = now - last_update
                if self._call_count >= self.ctl or \
                        age > self.ttl:
                    self._call_count = 1
                    raise AttributeError

                self._call_count += 1
                return value

            except (KeyError, AttributeError):
                value = self.func(*args)
                self.cache[args] = (value, now)
                return value

            except TypeError:
                return self.func(*args)
        return _memoized