Steven D'Aprano added the comment: The behaviour is as documented and is not a bug. When you have a three-argument extended slice, the starting and stopping values depend on whether the stride (step) is positive or negative. Although that's buried in a footnote to the table.
https://docs.python.org/3/library/stdtypes.html#common-sequence-operations The current behaviour is necessary so that the common case of both start and stop being blank is supported correctly for negative stride: py> "abcde"[::-1] 'edcba' So with a positive stride, your first example lst[0:3:-1] starts at index 0, ends at index 3, with step -1. That is an empty slice. But your second example lst[:3:-1] starts at the end of the list, index len(lst), ends at 3, with step -1. That is equivalent to lst[5:3:-1] which is not the same as your first example. ---------- nosy: +steven.daprano resolution: -> not a bug stage: -> resolved status: open -> closed _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue30137> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
