Comment on Python Performance: Why 'if not list' is 2x Faster Than Using len()

• gravitas_deficiency@sh.itjust.works ⁨6⁩ ⁨days⁩ ago

  My point is that the second statement you presented can have the effect of evaluating emptiness of a Sequence (note: distinct from an Iterable), but that only holds true if the target of the conditional IS a sequence. I’m underlining the semantic difference that was elided as a result of falsey evaluation.

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  • JasonDJ@lemmy.zip ⁨6⁩ ⁨days⁩ ago

    Ok, help a noob out. What is the difference between a sequence and an iterable? Is a sequence immutable, like a tuple?

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    • gravitas_deficiency@sh.itjust.works ⁨6⁩ ⁨days⁩ ago

      thing: Sequence[Any] iirc is iterable, indexable, and reversible.

      thing: Iterable[Any] only guarantees that its iterable.

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    • 48954246@lemmy.world ⁨6⁩ ⁨days⁩ ago

      An iterable is just something that can be iterated over, like range(10), or [1, 2, 3].

      A sequence on the other hand is a Collection that is reversible.

      docs.python.org/3/library/collections.abc.html#co…

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      • gravitas_deficiency@sh.itjust.works ⁨6⁩ ⁨days⁩ ago

        I know what an iterable is. But I am talking about Type[Iterable], which iirc does not obey falsey eval when empty.

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• BlackRoseAmongThorns@slrpnk.net ⁨6⁩ ⁨days⁩ ago

  Not really, generators have weird truthiness, i don’t remember if they evaluate to true or false, but they cannot be checked for emptiness so they default to either always true or always false.

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