livesubprocess 0.2.0

Displays the stdout and stderr of the subprocess in real time.

Live Subprocess

Displays the stdout and stderr of the subprocess in real time.

Advantage

• Displays subprocess stdout and stderr in real time as the process runs — not buffered until exit.
• Uses a PTY (pseudo-terminal) on POSIX so the child process keeps line-buffering active, just as it would in a real terminal.
• Cross-platform: PTY-based on POSIX, thread-backed pipe reader on Windows.
• Zero runtime dependencies.
• Async/await native; captures and returns the full output string for programmatic use.

Quickstart

Install:

pip install livesubprocess

Run a command with real-time output (POSIX):

import asyncio
from livesubprocess import LiveSubProcessFactory

async def main() -> None:
    pty = LiveSubProcessFactory.create_pty()
    stdout, returncode = await pty.run(["python", "-u", "script.py"])

asyncio.run(main())

Run a command with real-time output (POSIX and Windows):

import asyncio
import subprocess
from livesubprocess import LiveSubProcessFactory

async def main() -> None:
    proc = subprocess.Popen(
        ["python", "-u", "script.py"],
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
    )
    live = LiveSubProcessFactory.create_popen(proc)
    stdout, returncode = await live.wait()

asyncio.run(main())

PTY vs. Popen

	PTY (create_pty)	Popen (create_popen)
Platforms	POSIX only	POSIX and Windows
Process creation	Managed by livesubprocess	You create the Popen object
Line-buffering	Yes — child sees a real TTY	Depends on the child process
Use when	Simplest API on POSIX	Windows support needed, or you need to configure Popen directly (env, cwd, shell, etc.)

Both run() and wait() return (stdout_and_stderr: str, returncode: int).

How do I...

• Wrap an existing subprocess.Popen? Use LiveSubProcessFactory.create_popen(). This works on both POSIX and Windows.

  import asyncio
  import subprocess
  from livesubprocess import LiveSubProcessFactory
  
  async def main() -> None:
      proc = subprocess.Popen(
          ["ffmpeg", "-i", "input.mp4", "output.mp4"],
          stdout=subprocess.PIPE,
          stderr=subprocess.PIPE,
      )
      live = LiveSubProcessFactory.create_popen(proc)
      stdout, returncode = await live.wait()
  
  asyncio.run(main())
  

• Stop the reader early (before terminating the process)? Call live.stop() before popen.terminate() or popen.communicate() to deregister the fd readers cleanly.

Credits

This package was created with Cookiecutter and the yukihiko-shinoda/cookiecutter-pypackage project template.