How to check if turtle is running yet?

[Adorilson]

Hi, folks.

This is my first email (and question) here.

I'm a Brazilian professor and Phd student, and I'm developing a web environment to teach programming.

We are using Brython, and turtle is a central feature of my proposal.

Besides running the student code, I would like to check if it is correct.

If I have the code following:

```

for _ in range(4):

    turtle.forward(200)

    turtle.left(90)

print('End.')

```

'End.' will print before the square is done.

Here, I have two problems:

1. It sounds weird to a newbie to see a command result before the previous ones finished

2. How do I run the suite test only after the code's work is really done?

Is there an out-of-the-box solution for it? Is it possible to make turtle synchronous?

If not, what is the more suitable solution for "discover" if the turtle has done its work?

[]'s

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Adorilson

[Denis Migdal]

You want to use Brython in REPL mode ?

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[Denis Migdal]

Did you tried turtle.done() and screen.updated() ?

[Adorilson]

Em ter., 17 de mar. de 2026 às 06:45, Denis Migdal <denis....@gmail.com> escreveu:

Did you tried turtle.done() and screen.updated() ?

Yeah. And it isn't on the REPL.

The "problem" is that Brython creates a SVG which is rendered only after the "turtle.done()". 

Currently, I am binding a custom command in the end event of the "last" animation tag.

 Thank you.

To view this discussion visit https://groups.google.com/d/msgid/brython/749bb30c-24c4-4e82-99c7-ce017c6d6e65n%40googlegroups.com.

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Adorilson Bezerra

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[Denis Migdal]

How I see.

I assume this is due to turtle implementation in Brython.

Indeed, JS can't wait synchronously (e.g. sleep).

Maybe we could have a kind of :

JS.whenEndOfTimers( () => { do_stuff } ) ?

To view this discussion visit https://groups.google.com/d/msgid/brython/CADnwefF2hfjOsK7SnMnEPqk%2BT-8ECBGzfYgyFc5EPwMBZhPbRA%40mail.gmail.com.

[ben levitt]

It looks like the demo here: https://brython.info/gallery/turtle.html manages to animate.  Maybe you could start from that?

Ben

To view this discussion visit https://groups.google.com/d/msgid/brython/CAFr00W6meqv711PB1KCK-wvvBT54qk-up_Lp%2B0ggNcS8MH8yjw%40mail.gmail.com.

[Adorilson]

Em sex., 20 de mar. de 2026 às 05:14, Denis Migdal <denis....@gmail.com> escreveu:

How I see.

I assume this is due to turtle implementation in Brython.

Indeed, JS can't wait synchronously (e.g. sleep).

Maybe we could have a kind of :

JS.whenEndOfTimers( () => { do_stuff } ) ?

Yeah. To be more concrete, currently there is something like:

```python

g3 = document.querySelector('#turtle-canvas g:nth-child(3)')

animate = g3.lastChild.lastChild

animate.bind('endEvent', lambda ev: custom_command(params))

```

pitfall: the SVG tags (attributes' name case and some values) created by Firefox are different from those created by Chromium.  

To view this discussion visit https://groups.google.com/d/msgid/brython/CAFr00W6meqv711PB1KCK-wvvBT54qk-up_Lp%2B0ggNcS8MH8yjw%40mail.gmail.com.

[Ed]

The simple way is to just set a callback.  Use browser.timer.set_timeout (a thin wrapper around js function setTimeout) to suspend your code while turtle updates the canvas.  For fast operations, 100ms should be enough but adjust as needed:

from browser import timer

for _ in range(4):
    turtle.forward(200)
    turtle.left(90)

def callback () :
    print('End.')
browser.timer.set_timeout (callback, 100)

not as elegant as detecting when turtle is done.  but usually good enough.

there are also some animation frame functions in browser.timer.  never used them, don't know if they would help.

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