Streamlit: How to run subprocess with live stdout display on web UI
This example uses asyncio to run a subprocess and display its output live in a Streamlit web UI (while the command is still running). This is useful for long-running processes where you want to show the output as it comes in.
import streamlit as st
import asyncio
async def run_subprocess():
# Create placeholder for live output
output_placeholder = st.empty()
accumulated_output = []
process = await asyncio.create_subprocess_exec(
'ping', '-c', '10', '1.1.1.1',
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
)
# Read stdout stream
while True:
line = await process.stdout.readline()
if not line:
break
line = line.decode().strip()
accumulated_output.append(line)
# Update display with all output so far
output_placeholder.code('\n'.join(accumulated_output))
# Get any remaining output and errors
stdout, stderr = await process.communicate()
if stderr:
st.write("Subprocess errors:")
st.code(stderr.decode())
async def main():
st.write("Running subprocess...")
await run_subprocess()
if __name__ == '__main__':
asyncio.run(main())
