How do I get warnings.warn to issue a warning and not ignore the line?

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From the docs:

By default, Python installs several warning filters, which can be
overridden by the command-line options passed to -W and calls to
filterwarnings().

  • DeprecationWarning and PendingDeprecationWarning, and ImportWarning are ignored.
  • BytesWarning is ignored unless the -b option is given once or twice; in this case this warning is either printed (-b) or turned into
    an exception (-bb).

By default, DeprecationWarning is ignored. You can change the filters using the following:

warnings.simplefilter('always', DeprecationWarning)

Now your warnings should be printed:

>>> import warnings
>>> warnings.simplefilter('always', DeprecationWarning)
>>> warnings.warn('test', DeprecationWarning)
/home/guest/.env/bin/ipython:1: DeprecationWarning: test
  #!/home/guest/.env/bin/python

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