TypeError: 'NoneType' object is not subscriptable in Python class

Question

I'm making a program in Python with Turtle and encountered an error. I have no idea what I've done wrong and searched it up but could not pin point exactly were I messed up. I've dumbed down the code below so It's easier to understand.

Error:

  File "h:\turtletest.py", line 22, in onclick 
    x = pos[0]
TypeError: 'NoneType' object is not subscriptable

Code:

import turtle

tr = turtle.Turtle()
wn = turtle.Screen()
wn.setup(width=600,height=600)
wn.bgcolor("black")
wn.title("Turtle OnClick test")

class ExampleClass:
    def __init__(self, type_, width, height):
        self.width = width
        self.type_ = type_
        self.height = height

    def onclick(self):
        def get_xy(x, y):
            return (x, y)
        if self.type_ == "rect":
            pos = wn.onclick(get_xy)
            x = pos[0]
            y = pos[1]

            if x >= self.width and x <= self.width:
                print("Clicked!")
            else:
                pass

f = ExampleClass("rect", 25, 25)
f.onclick()

turtle.done()

Answer 1

I figured it out. I just modded the code slightly so that it's now in the actual function and not outside of it

def onclick(self):
        def main_func(x, y):
            print(x, y)
            if not x >= self.width and not x <= self.width:
                print("Clicked!")
            else:
                pass
        if self.type_ == "rect":
            scr.onclick(main_func)