Simple in-memory cache decorator with TTL

cached.py

def cached(ttl, cache={}):
    """
    A decorator for nullary functions that caches their results in memory for a
    given number of seconds.
    """
    def cached_decorator(f):
        key = f.__name__
        def decorated(*args, **kwargs):
            if key in cache:
                result, ts = cache[key]
                if time.now() - ts < ttl:
                    return result
            result = f(*args, **kwargs)
            cache[key] = (result, time.now())
            return result
        return decorated
    return cached