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Possible to distinguish between Sequence[str]/Iterable[str] and str? #1965

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Possible to distinguish between Sequence[str]/Iterable[str] and str?#1965

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@jtatum
jtatum
opened on Jul 29, 2016

If a function expects an iterable of strings, is it possible to forbid passing in a string, since strings are iterable? Seems like there are many cases where this would be an error, but I don't see an obvious way to check 't','h','i','s'.

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  1. jtatum
    changed the title [-]Possible to distinguish between Iterable[str] and str?[/-] [+]Possible to distinguish between Sequence[str]/Iterable[str] and str?[/+] on Jul 29, 2016

  2. gvanrossum commented on Jul 29, 2016

    @gvanrossum
    gvanrossum
    on Jul 29, 2016
    Member

    The PEP 484 type system currently can't express this, sorry. You'll have to start a discussion in the PEP 484 tracker: https://github.com/python/typing/

  3. gvanrossum
    closed this as completedon Jul 29, 2016
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