I'm not sure if this is an issue or by design, but this DeprecationWarning behaves differently to other DeprecationWarnings.

A normal DeprecationWarning triggered by code in __main__ is printed by default:

$ python -c 'import warnings; warnings.warn("test", DeprecationWarning)'
<string>:1: DeprecationWarning: test

But this one is silent:

$ python -c '"\,"'
[no output]

To see this DeprecationWarning at all, I need to type:

$ python -Wdefault -c '"\,"'
<string>:1: DeprecationWarning: invalid escape sequence '\,'

But that enables this DeprecationWarning for all modules, not just __main__ .

I've tested this with Python 3.9 on debian bullseye and the 3.10 docker image.