Make a function inside of another function

Question

I was wondering if you can make a function inside of another function in python. Just like this:

f().f2()

The f() is the first function, and f2() is the second function. Say f().f2() prints out "Hello world". But if I change the .f2() to .f3() it will print another string of text.

Is it possible?

You might want to check [classes](https://www.w3schools.com/python/python_classes.asp). — RiveN, Oct 18 '21 at 13:54
Yes, you just have to return an object from f that has callable f2 and f3 attributes. — jonrsharpe, Oct 18 '21 at 13:54
@RiveN I am not talking about classes, i am talking about how to add a function inside of another function. — Rydex, Oct 18 '21 at 13:55
@Rydex You might want to take a look into inner functions [here](https://stackoverflow.com/a/1589606/4224925). — xBurnsed, Oct 18 '21 at 13:58
I am trying to understand what you mean when you say "add a function inside of another function". Could you please elaborate. — sushant, Oct 18 '21 at 13:58
Perhaps a module is what you are after https://docs.python.org/3/tutorial/modules.html — JonSG, Oct 18 '21 at 17:26

score 2 · Accepted Answer · answered Oct 18 '21 at 13:54

2

Here's one approach:

def f():
    class F:
        @staticmethod
        def f2():
            print("Hello world")

        @staticmethod
        def f3():
            print("Another string of text")
    return F


f().f2()
f().f3()

answered Oct 18 '21 at 13:54

Samwise

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Yes, it works. But I think we should question OPs rational as it feels like an XY problem. – DeepSpace Oct 18 '21 at 13:56
Wonderful! the benefit of doing this is that your IDE can offer auto-completion hints apparently. – rv.kvetch Oct 18 '21 at 13:59
3

@rv.kvetch And the downside is that `F` will be redefined every single time `f` is called, which can have a high overhead – DeepSpace Oct 18 '21 at 14:01

score 2 · Answer 2 · answered Oct 18 '21 at 17:14

The other answers are good, but a simpler solution would be to make f a class. Since classes are callable, you can basically treat them as functions. The dot in f().f2() implies that f must return an object with an f2 attribute, and a class can do just that:

class f:

    def f2(self):
        print("Hello world")

    def f3(self):
        print('another string of text')

score 1 · Answer 3 · answered Oct 18 '21 at 14:01

I like Samwise answer better, but here's a way of doing it without classes, if you really wanted to:

def f():
    def f2():
        print("Hello world")

    def f3():
        print("Another string of text")

    for func_name, func in locals().items():
        setattr(f, func_name, func)

    return f


f().f2()
f().f3()

score 0 · Answer 4 · edited Oct 19 '21 at 03:18

0

def f():
    class F:
        @staticmethod
        def f_2():
            print("something")

        @staticmethod
        def f_3():
            print("something 2")
    return F


f().f_2()
f().f_3()

edited Oct 19 '21 at 03:18

Gino Mempin

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answered Oct 18 '21 at 14:00

Marko

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Make a function inside of another function

4 Answers4