function with one argument called without any argument in python

Question

I read this code in codeskulptor3

import simplegui

message = "Welcome!"

def click():
  global message
  message = "Good job!"


def draw(canvas):
  canvas.draw_text(message, [50,112], 48, "Red")

frame = simplegui.create_frame("Home", 300, 200)
frame.add_button("Click me", click)
frame.set_draw_handler(draw)
frame.start()

I don't understand why the function draw is being passed to set_draw_handler without any argument (it should take a canvas object). But I don't see any canvas object. Who pass it?

Because **the function** is passed, **not** the result of calling it. — Karl Knechtel, Dec 30 '22 at 23:12
You're telling set_draw_handler "Hey, here's this function, I want you to call it **later**". — John Gordon, Dec 30 '22 at 23:15

score -1 · Answer 1 · answered Dec 30 '22 at 23:12

-1

frame is taking draw as a callback, and will call it and pass the canvas argument at appointed times.

answered Dec 30 '22 at 23:12

starball

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But I don't see any canvas argument? Who pass it? – Ryu10 Jan 01 '23 at 09:41

function with one argument called without any argument in python

1 Answers1