threading

At a glance

The community member is trying to use a long-living thread in their notebook, but the while loop in the example code only runs once. The community members discuss potential issues and solutions, including a bug in the output, using bar.join() to keep the output in the cell, and the problem with using time.sleep() in a thread. The community members identify the issue with time.sleep() causing the thread to stop, and a contributor is helping to fix the issue. The community members also want to give scientists the ability to start and stop a separate process, such as capturing images from a camera, with a button click, and using bar.join() worked for this use case.

kkobe

Hello, i want to use a long living thread in my notebook. I dumbed it down to this basic example:

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import threading
import time
threading.Thread = mo.Thread

def run_long():
    while True:
        print("looping")
        time.sleep(1)

bar = threading.Thread(target=run_long)
bar.start()

When i run this cell, looping is only printed once (it looks like the while loop stop after one iteration).

6 comments

MMyles Scolnick

hmm that seems like a bug. I see it printing out to my terminal, but not the marimo output. we can look into fixing this.

MMyles Scolnick

we can look into this. out of curiosity, what are you looking to do with the thread? e.g. pull data, refresh, etc.

SShahmir

not sure if this solves your issue, but a bar.join() could help. The output would be kept in the cell / different cell.

kkobe

We want to give scientists the ability to start a seperate process (in our case, start capturing images from a camera) and stop it with a click on a button.

Using bar.join() worked, thanks!

kkobe

update

After some searching, I found the problem lies in the use of time.sleep() in a thread. The thread seems to stop after a time.sleep()

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import threading
import time

# Override the Thread class with a custom Thread class
threading.Thread = mo.Thread

def run_thread_with_sleep():
    print("bar")
    time.sleep(2)
    print("foo")
        
# Create a new thread that runs the function
foo = threading.Thread(target=run_thread_with_sleep)
foo.start()

This code prints bar but not foo

MMyles Scolnick

there was another issue about this. we've identified the fix and a contributor is helping out fixing it. (the thread is still running, but the stdio does get detached)

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