What is exactly passed as an argument if we pass Python function name?

Question

Recently I was describing my code to my Uni teacher, it was something like this:

def f(x):
    return x*x

def map_list(function, list):
    return [function(element) for element in list]

map_list(f, [1,2,3])

and I told that in map_list(f, [1,2,3]), f argument is a pointer to the function, which is obviously wrong, as there are no pointers really in PYthon. I was trying to figure it out, but I couldn't find any clear answer. So, what is it? Reference, object, or something else?

Thanks in advance.

It's a reference to a function, as every name in Python is a reference to an object. — Klaus D., Jun 21 '20 at 10:24

score 2 · Accepted Answer · answered Jun 21 '20 at 10:25

2

Functions are first-class objects in python and as such you can pass them into functions and place them in lists, dictionaries etc. They are getting passed as object references.

answered Jun 21 '20 at 10:25

bhristov

3,137
2
10
26

score 0 · Answer 2 · answered Jun 21 '20 at 10:32

What you pass is a name which is bind to an object. You can have several names bind to the same object, as in this example:

x = []
y = x # x and y are two names bind to the same object

If you call a function with a parameter you create another name (the name of the argument) bind to the passed object.

In your case the function map_list accepts everything that is callable with (). This means you can pass anything which has implemented the __call__() method. This is of course also the case for a function.

What is exactly passed as an argument if we pass Python function name?

2 Answers2