cache = dict()

def memoize(func):
    def wrapper(*args, **kwargs):
        if (args, frozenset(kwargs.items())) not in cache:
            #print("If I uncomment this then CALLING f 2 is printed, otherwise not")
            cache[(args, frozenset(kwargs.items()))] = func(*args, **kwargs)
        return cache[(args, frozenset(kwargs.items()))]
    return wrapper

@memoize
def f(x):
    print("CALLING: f {}".format(x))
    return x ** 2