A blog post on choosing more specific types rather than general ones like list and dict.

  • qwertyasdef@programming.dev
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    1 year ago

    If you don’t need to reuse the collection or access its items out of order, you can also use Iterable which accepts even more inputs like generators.

  • o11c@programming.dev
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    1 year ago

    The problem is that there’s a severe hole in the ABCs: there is no distinction between “container whose elements are mutable” and “container whose elements and size are mutable”.

    (related, there’s no distinction for supporting slice operations or not, e.g. deque)

  • jadelord
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    1 year ago

    Good point, and Łukasz Langa mentioned this in his talk (check it out). He names it the robustness principle, in his words (around 22:20 mark:

    “Vague in what you accept, concrete in what you return”

    But he also mentions some gotchas like how Iterable[str] can backfire, because str is also an Iterable[str] and it might be better to use list[str].

  • coffeewithalex@lemmy.world
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    1 year ago

    The important difference is that you don’t need to import anything in order to quickly use list type. This wins in the majority of the cases, unless I’m building something that will be imported by multiple other modules and it really pays to be that explicit.

    • MeadSteve@reddthat.comOP
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      1 year ago

      That was definitely a nice feature (I forget exactly when list over List was added). That said I’ve never really been bothered about having imports. Especially when I know the import is side effect free like the typing module. But I definitely use import free list for script files without many lines of code.

  • chemacortes@programming.dev
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    1 year ago

    Sequence now lives at collections.abc. BTW, float is not a supertype of int (issubclass(int, float) == False). Normaly, It is acceptable to use int instead of float, but speaking of variance, it is more precise to use numbers.Real:

    issubclass(Integral, Real) == True
    issubclass(int, Real) == True
    issubclass(float, Real) == True
    issubclass(complex, Real) == False