Python subprocesses with closed stdio

stdio_closed.py

import os
import subprocess
import sys

PRINT_STDERR_REPR_PY = 'import sys; print(f"    {sys.stderr=}\\n")'

print('Child stderr -> our stderr')
subprocess.run([sys.executable, '-c', PRINT_STDERR_REPR_PY])

print('Child stderr -> /dev/null')
subprocess.run([sys.executable, '-c', PRINT_STDERR_REPR_PY], stderr=subprocess.DEVNULL)

print('Child stderr closed by shell')
subprocess.run(f"{sys.executable} -c '{PRINT_STDERR_REPR_PY}' 2>&-", shell=True)

print('Child stderr -> a closed file object/descriptor')
pid = os.posix_spawn(
    sys.executable,
    [sys.executable, '-c', PRINT_STDERR_REPR_PY],
    os.environ,
    file_actions=[(os.POSIX_SPAWN_CLOSE, 2)],
)
_, status = os.waitpid(pid, 0)
assert status == 0

print("Child stderr -> parent's closed sys.stderr object")
subprocess.run([sys.executable, '-c', PRINT_STDERR_REPR_PY])

print("Child stderr -> parent's closed stderr descriptor")
os.close(2)
subprocess.run([sys.executable, '-c', PRINT_STDERR_REPR_PY])

Note the cases where sys.stderr == None in the child process

$ python stdio.py
Child stderr -> our stderr
    sys.stderr=<_io.TextIOWrapper name='<stderr>' mode='w' encoding='utf-8'>

Child stderr -> /dev/null
    sys.stderr=<_io.TextIOWrapper name='<stderr>' mode='w' encoding='utf-8'>

Child stderr closed by shell
    sys.stderr=None

Child stderr -> a closed file object/descriptor
    sys.stderr=None

Child stderr -> parent's closed sys.stderr object
    sys.stderr=<_io.TextIOWrapper name='<stderr>' mode='w' encoding='utf-8'>

Child stderr -> parent's closed stderr descriptor
    sys.stderr=None