[3.11] gh-87452: Improve the Popen.returncode docs by miss-islington · Pull Request #103771 · python/cpython
.. attribute:: Popen.returncode
The child return code, set by :meth:`poll` and :meth:`wait` (and indirectly by :meth:`communicate`). A ``None`` value indicates that the process hasn't terminated yet. The child return code. Initially ``None``, :attr:`returncode` is set by a call to the :meth:`poll`, :meth:`wait`, or :meth:`communicate` methods if they detect that the process has terminated.
A ``None`` value indicates that the process hadn't yet terminated at the time of the last method call.
A negative value ``-N`` indicates that the child was terminated by signal ``N`` (POSIX only).