CODEWITHSUNDEEP
pythondjangopython-2.7django-models
Denny Sugianto
Denny Sugianto

Reputation: 9

what is a function inside a function in django/python

I wanna know, what is main idea function inside a function in djanggo?, something like this example.

def partition_by_mod(base):
    def func(n):
        return n % base
    return staticmethod(func)

when I call this function like this test = partition_by_mod(8), so I'm wondering where the "n" comes from.

thank you ~

Upvotes: 0

Views: 54

Answers (1)

John Bollinger
John Bollinger

Reputation: 180266

what is main idea function inside a function in djanggo?

It's the same as a function defined anywhere else, but it is accessible by name only within the outer function, and it closes over the variables (such as base) of the scope in which it is defined, so that they are indirectly accessible to whomever calls the function. Your particular example could be replaced by a lambda:

def partition_by_mod(base):
    return staticmethod(lambda n: n % base)

when I call this function like this test = partition_by_mod(8), so I'm wondering where the "n" comes from.

The argument is provided by the code that actually calls the function. Note in particular that

    staticmethod(func)

does not call func, but rather passes func itself as an argument, presumably with the idea that staticmethod will call it. This is sometimes described as a "callback function". You can recognize a function call by the parenthesized argument list, which is required even when there are zero arguments. If and when staticmethod does call it, staticmethod has the responsibility to provide the needed argument.

Upvotes: 1

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