Streamlit subprocess streaming output to the web page / redirect std out

gistfile.py

""" 
Run subprocess command and stream output to the web page

streamlit run web_ui.py --server.port 10006 --browser.gatherUsageStats False

streamlit >=1.30

# print_numbers.py
import time

for i in range(1, 200):
    print(i)
    time.sleep(0.01)
"""
import streamlit as st
import subprocess
from typing import List

def run_command_and_stream_output(
    command: List[str],
    expander_name: str = "Log",
    expanded: bool = False,
    height: int = 200,
    max_log_lines: int = 100,
) -> None:
    """run subprocess command and stream output to the web page

    Attention:
        - for python script, you need to add `-u` argument force the stdout and stderr streams to be unbuffered
            - for example: `command = ["python", '-u', 'print_numbers.py']`

    Args:
        command (List[str]): command to run
        expander_name (str): name of the expander
        expanded (bool): whether the expander is expanded
        height (int): height of the expander
        max_log_lines (int): maximum number of lines to display in the log

    Raises:
        Exception: if the command returns non-zero exit status

    Examples:
        >>> run_command_and_stream_output(["python", "-u", "print_numbers.py"])

    """
    process = subprocess.Popen(
        command,
        stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT,
        universal_newlines=True,
    )

    log = []

    with st.expander(expander_name, expanded=expanded):
        with st.container(height=height):
            log_placeholder = st.empty()

    while process.poll() is None:
        line = process.stdout.readline()
        if not line:
            continue
        log.append(line.strip())
        if len(log) > max_log_lines:
            log.pop(0)
        log_placeholder.code("\n".join(log), line_numbers=True)

    if process.returncode != 0:
        st.error(f"Error: {process.returncode}")
        raise Exception(
            f"Command '{' '.join(command)}' returned non-zero exit status {process.returncode}"
        )



if __name__ == "__main__":
    start_button = st.button("Run External Script")

    if start_button:
        command = ["python", "-u", "print_numbers.py"]
        run_command_and_stream_output(command)
        st.success("Script has been executed successfully")