Python class decorator arguments

Question

I\'m trying to pass optional arguments to my class decorator in python. Below the code I currently have:

class Cache(object):
    def __init__(self, function         


        

Answer 1

@Cache
def double(...): 
   ...

is equivalent to

def double(...):
   ...
double=Cache(double)

While

@Cache(max_hits=100, timeout=50)
def double(...):
   ...

is equivalent to

def double(...):
    ...
double = Cache(max_hits=100, timeout=50)(double)

Cache(max_hits=100, timeout=50)(double) has very different semantics than Cache(double).

It's unwise to try to make Cache handle both use cases.

You could instead use a decorator factory that can take optional max_hits and timeout arguments, and returns a decorator:

class Cache(object):
    def __init__(self, function, max_hits=10, timeout=5):
        self.function = function
        self.max_hits = max_hits
        self.timeout = timeout
        self.cache = {}

    def __call__(self, *args):
        # Here the code returning the correct thing.

def cache_hits(max_hits=10, timeout=5):
    def _cache(function):
        return Cache(function,max_hits,timeout)
    return _cache

@cache_hits()
def double(x):
    return x * 2

@cache_hits(max_hits=100, timeout=50)
def double(x):
    return x * 2

PS. If the class Cache has no other methods besides __init__ and __call__, you can probably move all the code inside the _cache function and eliminate Cache altogether.