turtle.ontimer(None, 8000) freezes the screen

Python Help
1

I’m writing a tutorial with Turtle. I’ve used some snippet code to scaffold the students’ work.

I’ve written pieces of stuff like:

turtle.onkey(None, 'Down')
turtle.ontimer(None, 4000)

Despite None not being callable, this works fine. Except that ontimer causes a screen freeze for 4000 ms (in this case).

After a dive into the source code, I found these lines.

# I'd rather use time.sleep(ms*0.001)
self.tk.call('after', ms)

So, this freezing seems like a feature. So, the question is: Why? What’s the reason behind that? Why not just return None ?

And where can I see the call’s documentation? Is this ‘after’ the same function where these lines are on, or a predefined value for call?

2

That code in Tkinter is a wrapper for Tcl/Tk’s after command, which is documented in the Tcl manual.

It seems to be basically the same thing as time.sleep when called without a callback. I don’t know if or why one would be preferable to the other. The comment about rather using time.sleep was apparently added by Guido van Rossum 30 years ago.

3

Thank you, @tunedal .

Really, after’s definition makes cleaning you can call it without a callback function:

def after(self, ms, func=None, *args):

However, it isn’t possible on turtle.ontimer. Might we do something there, at least fix the documentation about None.