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Comment by BerislavLopac | Hacker News Reader

I believe the recent idiomatic recommendation for the first two is to use the union type expression:

  1. T | None
  2. SuccessT | FailureT

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This is potentially quite helpful, but would you happen to have a source for that?

The Union Type PEP[0] suggests that the "bitwise or" syntax is equivalent, but cleaner than typing.Union

[0]: https://docs.python.org/3/library/stdtypes.html#types-union

Thanks! I missed that.

They're both perfectly valid; but the expression style [0] is shorter and more obvious, especially compared to Optional. Even the documentation for Optional states [1]:

  Note that this is not the same concept as an optional argument, which is one that has a default.

[0] https://docs.python.org/3.11/library/stdtypes.html#types-uni...

[1] https://docs.python.org/3.11/library/typing.html#typing.Opti...

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