Is there a preferred style for creating closures in python?

Question

Is either of the two styles preferred or more "pythonic" for creating closures (edit: "closure-like objects")?

def make_doer(closed_var):
    def doer(foo):
        pass  # Do something with closed_var and foo

    return doer

class Doer:
    def __init__(self, closed_var):
        self._closed_var = closed_var

    def __call__(self, foo):
        pass  # Do something with self._closed_var and foo

The only differences I can tell are that the former is a tiny bit shorter but the second has an advantage in that the docstring for the resulting function (__call__ in the second case) is less nested/hidden. Neither seems like a huge deal, anything else that would tip the balance?

The second isn't a closure. It is a class with state. [It is a poor man's closure](https://stackoverflow.com/questions/2497801/closures-are-poor-mans-objects-and-vice-versa-what-does-this-mean). In Python, we are rich and have both. Being a bit more serious, you are creating two different things. In the first, `make_doer` returns *a function object*, in the second, `Doer` returns *a `Doer` object*. — juanpa.arrivillaga, Jun 19 '20 at 22:48
You are correct @juanpa.arrivillaga, updated to say "closure-like" :) — Luis, Jun 20 '20 at 02:11

score 0 · Answer 1 · answered Jun 19 '20 at 22:31

Closures have to do with maintaining references to objects from scopes that have passed, or from earlier scopes.

Here is the simplest example of the form a Closure takes:

def outer(): 
    x=7

    def inner(y):
        return x + y

    return inner

i = outer()

Is there a preferred style for creating closures in python?

1 Answers1