Pass an object's function as parameter to another function

Question

I have function that will get the data from the cache if it exists else it will query the DB and save it in the cache.

def get_ref_from_cache_or_db(obj, key, duration=60):
data = get_routes_from_cache(key=key)
if data:
    response = json.loads(data)
else:
    response = obj.fetch().to_dict()
    set_routes_to_cache(key=key, duration=duration, value=json.dumps(response))
return response

Sometimes I have to return different results from the same object, for example I need to call

response = obj.fetch().to_dict()

or

response = obj.fetch().to_other_dict()

If it were a simple simple function call my code would simply be:

def get_ref_from_cache_or_db(func, key, duration=60):
    data = get_routes_from_cache(key=key)
    if data:
        response = json.loads(data)
    else:
        response = func()
        set_routes_to_cache(key=key, duration=duration, value=json.dumps(response))
    return response

But in this case I don't know how to pass the function that will be called from the object returned from another function, i.e i want to call something like this get_ref_from_cache_or_db(obj.fetch.to_dict, key, duration). I don't want to call the fetch() beforehand because it will always get the data from the DB.

pygame · Accepted Answer · 2021-04-30 07:39:26Z

1

If you want to call the fetch() only when needed, you can use a lambda: get_ref_from_cache_or_db(lambda: obj.fetch().to_dict() , key, duration)

answered Apr 30, 2021 at 7:39

pygame

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2 Comments

Mehdi Khlifi Over a year ago

Can you please explain more how this works?

pygame Over a year ago

A lambda is a one liner function definition, so here you create a function that calls your function. I would suggest to read more about lambdas.

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