this post was submitted on 24 Apr 2025
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Python Performance: Why 'if not list' is 2x Faster Than Using len() (blog.codingconfessions.com)
submitted 22 hours ago by jnovinger to c/python
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[–] Kissaki 6 points 11 hours ago (1 children)

While the 2nd approach is not wrong, the first method is considered more Pythonic. Many people don’t agree, but I’ve already put forward my points in a previous article on that debate.

Does Pythonic mean best practice in the python community or "good python"?

If "many people don't agree", how can they claim it to be "pythonic"? Isn't that contradictory?

[–] [email protected] 1 points 7 hours ago* (last edited 7 hours ago)

"Many" isn't the same as "most," though I don't think there's any way to know what "most" is.

But here's my reason for agreeing w/ the OP:

  • not x checks both None and emptiness, which is usually desired
  • len(x) == 0 will raise an exception if x is null
  • with type hinting, those should be the only two reasonable options

It's nice that it's slightly faster, though performance has absolutely nothing to do w/ my preference, though it does have something to do with my preference for avoiding exceptions for non-exceptional cases.