Python method vs function [duplicate]

Question

I am seeking for a confirmation if my thinking is correct in terms of Python method vs function:

A method is a part of a class.

A function is defined outside of a class.

so e.g.

class FooBar(object):
    def __init__(self):
        pass
    def foo(self):
        pass


def bar():
    pass


if __name__ == '__main__':
    fb = FooBar()

I understand def foo defines method and def bar defines function. Am I correct?

Answer 1

Yes. To be clear, methods are functions, they are simply attached to the class, and when that function is called from an instance it gets that instance passed implicitly as the first argument automagically*. It doesn't actually matter where that function is defined. Consider:

class FooBar:
    def __init__(self, n):
        self.n = n
    def foo(self):
        return '|'.join(self.n*['foo'])


fb = FooBar(2)

print(fb.foo())

def bar(self):
    return '*'.join(self.n*['bar'])

print(bar(fb))

FooBar.bar = bar

print(fb.bar())

---

*I highly recommend reading the descriptor HOWTO. Spoiler alert, Functions are descriptors. This is how Python magically passes instances to methods (that is, all function objects are descriptors who's __get__ method passes the instance as the first argument to the function itself when accessed by an instance on a class!. The HOWTO shows Python implementations of all of these things, including how you could implement property in pure Python!