gh-141984: Reword and reorganize Subscription (and Slicing) docs #141985
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Co-authored-by: Blaise Pabon <blaise@gmail.com>
Co-authored-by: Blaise Pabon <blaise@gmail.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
Co-authored-by: Blaise Pabon <blaise@gmail.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
encukou
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Dec 3, 2025
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encukou
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Thank you for going through this!
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StanFromIreland
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Just a few little things, overall looks very good!
| the ``3`` in ``items[3]``. | ||
| Usually used to select an element of a container. | ||
| Also called a :term:`key` when subscripting a :term:`mapping`, | ||
| or :term:`index` when subscripting a :term:`sequence`. |
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| or :term:`index` when subscripting a :term:`sequence`. | |
| or an :term:`index` when subscripting a :term:`sequence`. |
| subscription: `primary` '[' `subscript` ']' | ||
| subscript: `slice` | `tuple_slices` | ||
| tuple_slices: ','.(`slice` | `starred_expression`)+ [','] | ||
| slice: `proper_slice` | `assignment_expression` |
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By this grammar, if one does something[0], 0 is an int and is a slice, but that contradicts with your glossary entry, that states it must be a "an object of type slice"?
| Note that no error is raised if a slice position is less than zero or larger | ||
| than the length of the sequence. | ||
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| If *start* is missing or ``None``, slicing behaves as if *start* was zero. |
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| If *start* is missing or ``None``, slicing behaves as if *start* was zero. | |
| If *start* is missing or :data:`None`, slicing behaves as if *start* was zero. |
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This merges the Subscriptions and Slicings sections in the language reference. From the parser's point of view, slicing is a special case of subscription, and it makes sense to document it that way too.
The PR also touches Data model documentation: I've tried to move details of the runtime behaviour there, and to de-duplicate (and cross-link) as needed.
Similar for the
sliceattribute docs.Todo:
📚 Documentation preview 📚: https://cpython-previews--141985.org.readthedocs.build/