https://github.com/python/cpython/commit/c2276176d543a2fc2d57709c2787f99850fbb073 commit: c2276176d543a2fc2d57709c2787f99850fbb073 branch: main author: Adorilson Bezerra <[email protected]> committer: terryjreedy <[email protected]> date: 2024-03-25T18:34:20-04:00 summary:
Add information about negative indexes to sequence datamodel doc (#110903) Co-authored by Terry Jan Reedy files: M Doc/reference/datamodel.rst diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 75b656f385d34b..bc835b8e30cb29 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -299,14 +299,17 @@ Sequences These represent finite ordered sets indexed by non-negative numbers. The built-in function :func:`len` returns the number of items of a sequence. When the length of a sequence is *n*, the index set contains the numbers 0, 1, -..., *n*-1. Item *i* of sequence *a* is selected by ``a[i]``. +..., *n*-1. Item *i* of sequence *a* is selected by ``a[i]``. Some sequences, +including built-in sequences, interpret negative subscripts by adding the +sequence length. For example, ``a[-2]`` equals ``a[n-2]``, the second to last +item of sequence a with length ``n``. .. index:: single: slicing Sequences also support slicing: ``a[i:j]`` selects all items with index *k* such that *i* ``<=`` *k* ``<`` *j*. When used as an expression, a slice is a -sequence of the same type. This implies that the index set is renumbered so -that it starts at 0. +sequence of the same type. The comment above about negative indexes also applies +to negative slice positions. Some sequences also support "extended slicing" with a third "step" parameter: ``a[i:j:k]`` selects all items of *a* with index *x* where ``x = i + n*k``, *n* _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: [email protected]
