Title: Clarify that Popen.returncode does not get auto-set when the process terminates
Type: Stage:
Components: Documentation Versions: Python 3.10
Status: open Resolution:
Dependencies: Superseder:
Assigned To: docs@python Nosy List: Antony.Lee, docs@python
Priority: normal Keywords:

Created on 2021-02-21 15:56 by Antony.Lee, last changed 2021-02-21 15:56 by Antony.Lee.

Messages (1)
msg387463 - (view) Author: Antony Lee (Antony.Lee) * Date: 2021-02-21 15:56
Currently, the documentation for Popen.returncode states

    The child return code, set by poll() and wait() (and indirectly by communicate()). A None value indicates that the process hasn’t terminated yet.

    A negative value -N indicates that the child was terminated by signal N (POSIX only).

As far back as it had been suggested that this fails to emphasize an important piece of information, namely that this attribute can be outdated (it is *only* set if poll() or wait() are called; this is not obvious, e.g. returncode could have beeen implemented as a property that auto-calls poll()).  I do realize that a strict reading of the docs does suggest the actual behavior, but a bit of explicitness won't hurt...

The wording suggested in seems clearer to me ("Note: The value stored in returncode may be out-of-date. Use poll() to reliably find the current return code.").
Date User Action Args
2021-02-21 15:56:24Antony.Leecreate