Function that has access to self, inside a class method

June 6, 2023

How to define a function, inside a class method (for example for a threading Thread target function), that needs access to self?
Is the solution 1. correct or should we use 2.?

import threading, time
class Foo:
    def __init__(self):
        def f():
            while True:
                print(self.a)                
                self.a += 1
                time.sleep(1)
        self.a = 1
        threading.Thread(target=f).start()
        self.a = 2
Foo()

It seems to work even if self is not a parameter of f, but is this reliable?

import threading, time
class Foo:
    def __init__(self):
        self.a = 1
        threading.Thread(target=self.f).start()
        self.a = 2
    def f(self):
        while True:
            print(self.a)                
            self.a += 1
            time.sleep(1)
Foo()

This is linked to Defining class functions inside class functions: Python but not 100% covered by this question.

>Solution :

The first is fine; f is redefined every time you call __init__, but as it is local to __init__, it has access to the entire local scope of __init__, including the name self.

Whether __init__ should be starting a new thread is another matter.