warnings is a pretty cheap import, so the import-time saving from deferring it is usually pretty minimal. However, it's also a textbook example of an import that should be deferred wherever reasonable. Most of the time, it's only imported so that aDeprecationWarning can be emitted, and we should try to make it so that users only have to pay the (small) performance penalty from it being imported if they actually hit the specific code path that's deprecated.

Nonetheless, since the performance impact of importingwarnings is so small, I've tried to avoid modules that make multiple uses ofwarnings -- it's not particularly DRY to have import warnings repeated several times in the same module. The one exception I made here isargparse:argparse really should be importing the absolute minimum set of modules given that it's a CLI framework (see#74338 for previous discussion).

• Issue:Improve import time of various stdlib modules #109653