threader

Streamlit Extras Threader

Utility functions to make running threading.Threads easy in streamlit.

Basic usage

This requires runOnSave = true in ./streamlit/config.toml, and you will need to create an empty file named reruntrigger.py in the root of your project.

import time
import streamlit as st
import reruntrigger_default # This is required so the watcher can rerun from this file
from streamlitextras.threader import lock, trigger_rerun, \
                                     streamlit_thread, get_thread, \
                                     last_trigger_time

def main():
    thread_name = streamlit_thread(my_threaded_function, (5,))
    st.write("This should be here before my_threaded_function() is done!")
    st.button("Thread info", on_click=button_callback, args=(thread_name,))

def button_callback(thread_name):
    # Sometimes streamlit will trigger button callbacks when re-running,
    # So we block them if we triggered a rerun recently
    if last_trigger_time() < 1:
        return
    my_thread = get_thread(thread_name)
    st.write(my_thread) # threading.Thread

def my_threaded_function(time):
    time.sleep(time)
    with lock:
        # Do something that might interfere with other threads,
        # file operations or setting st.session_state
        pass
    print(f"Thread done! I slept for {time} seconds.")

if __name__ == "__main__":
    main()

Advanced usage

Mostly you may want to use streamlit_thread(my_threaded_function, rerun_st=False) if you don't want streamlit to rerun after the thread.

NOTE The rerun trigger will rerun all streamlit sessions for all users on your site.

To get around this, generate or use a unique id you have for each user session, use it in this modules function arguments and then import the rerun trigger for that session e.g.

import importlib
unique_id = st.session_state.get("session_uid", generate_uniqueid())
st.session_state["session_uid"] = unique_id
importlib.import_module(f"reruntrigger_{unique_id}")


from streamlitextras.threader import trigger_rerun
st.button("Rerun for this session only", on_click=trigger_rerun, args=(unique_id,))

See the API docs or the source file for function argument reference.