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gh-155856: Rephrase doc for "iter" to avoid "collection" #155857

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gh-155856: Rephrase doc for "iter" to avoid "collection" #155857

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7 changes: 3 additions & 4 deletions Doc/library/functions.rst
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Expand Up @@ -1147,10 +1147,9 @@ are always available. They are listed here in alphabetical order.

Return an :term:`iterator` object. The first argument is interpreted very
differently depending on the presence of the second argument. Without a
second argument, the single argument must be a collection object which supports the
:term:`iterable` protocol (the :meth:`~object.__iter__` method),
or it must support
the sequence protocol (the :meth:`~object.__getitem__` method with integer arguments
second argument, the single argument must be an object that supports the
:term:`iterable` protocol (the :meth:`~object.__iter__` method) or the
:term:`sequence` protocol (the :meth:`~object.__getitem__` method with integer arguments

@StanFromIreland StanFromIreland Aug 15, 2026

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Linking to the sequence glossary entry isn't quite correct here, it has stricter requirements (i.e., a __len__ method) than iter()'s requirements.

@picnixz picnixz Aug 15, 2026

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Oh we have a discrepancy between Sequence protocol in collections.abc and the one in C then: https://docs.python.org/3/c-api/sequence.html#c.PySequence_Check

@picnixz picnixz Aug 15, 2026

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Also, we say:

The sequence iteration protocol (used, for example, in for loops), expects that an IndexError will be raised for illegal indexes to allow proper detection of the end of a sequence.

So I'km not sure you need __len__

@picnixz picnixz Aug 15, 2026

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Actually, I think it's the C page which should mentions the __len__ as well.

starting at ``0``). If it does not support either of those protocols,
:exc:`TypeError` is raised. If the second argument, *sentinel*, is given,
then the first argument must be a callable object. The iterator created in this case
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