I want to use python to minic bash command ./script.sh &> /tmp/my.log &, but with Python code able to modify the lines before they’re written to the output file.

import subprocess
import threading
import sys

log_file = sys.argv[1]
program_and_args = sys.argv[2:]

with open(log_file, 'w') as log:
    process = subprocess.Popen(program_and_args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True, start_new_session=True)
    print(f"Background process started. PID: {process.pid}")

    def capture_output():
        lineno = 1 # example, real logic more complicated
        for line in process.stdout:
            log.write(f'{lineno}: {line}')
            log.flush()
            lineno += 1
        process.wait()

    # capture_output()

    thread = threading.Thread(target=capture_output, daemon = True)
    thread.start()

print("Main program continuing...")

Although the above python program can run as below.

./main.py /tmp/my.log ./script.sh

But nothing is written in /tmp/my.log. How can I fix the python program so that it has the same effect as the bash command ./script.sh &> /tmp/my.log & with the addition of being able to modify the content with arbitrary Python code?