subprocess.run() and subprocess.Popen() accepts a cwd= parameter to change directory before running the subprocess.

Unfortunately it's not possible to use a file descriptor to run the subprocess in a directory already opened.

For example:

    import os
    import subprocess
    with os.open('/usr/bin', os.O_RDONLY) as f:
        subprocess.run(["ls", "-l"], cwd=f, check=True)

fails with

    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib/python3.9/subprocess.py", line 505, in run
        with Popen(*popenargs, **kwargs) as process:
      File "/usr/lib/python3.9/subprocess.py", line 951, in __init__
        self._execute_child(args, executable, preexec_fn, close_fds,
      File "/usr/lib/python3.9/subprocess.py", line 1754, in _execute_child
        self.pid = _posixsubprocess.fork_exec(

Using a file descriptor instead of path is useful to address TOCTOU issues.

Maybe a mean to convert a file descriptor to a Path-like object would do the trick.