IMO, there're lots of use cases in parsing related stuffs, which requires rindex a lot, say, when you have generated a tokenizer which might across multiple lines:
line 8: X """ line 9: line 10: """ In this case, we need to extract 2 tokens X and , a multiline whitespace string. After getting each token we're to compute/update the current column and line number. If the line number gets advanced then we use rindex('\n') to help with updating the new column number, otherwise, col_offset += len(current_token) . However, the reason why we don't need list.rindex but do for str.rindex is simple I'd say: str is immutable and has no O(1) reverse method. On the other hand, when it comes to list, you can use list.index after list.reverse, and after a bunch of operations you can resume the state by invoking list.reverse again. On Wed, Apr 24, 2019, 12:11 AM <python-ideas-requ...@python.org wrote: > Send Python-ideas mailing list submissions to > python-ideas@python.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://mail.python.org/mailman/listinfo/python-ideas > or, via email, send a message with subject or body 'help' to > python-ideas-requ...@python.org > > You can reach the person managing the list at > python-ideas-ow...@python.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Python-ideas digest..." > Today's Topics: > > 1. What are the strong use cases for str.rindex()? (???) > > > > ---------- Forwarded message ---------- > From: "林自均" <johnl...@gmail.com> > To: python-ideas@python.org > Cc: > Bcc: > Date: Tue, 23 Apr 2019 14:44:25 +0800 > Subject: [Python-ideas] What are the strong use cases for str.rindex()? > Hi all, > > I found that there are str.index() and str.rindex(), but there is only > list.index() and no list.rindex(). So I filed the issue > https://bugs.python.org/issue36639 to provide list.rindex(). However, the > issue was rejected and closed with the comment: > > > There were known, strong use cases for str.rindex(). The list.rindex() > method was intentionally omitted. AFAICT no compelling use cases have > arisen, so we should continue to leave it out. In general, we don't grow > the core APIs unnecessarily. > > However, I am not sure what the known, strong use cases for str.rindex() > are. Why doesn't the strong use cases apply on list.rindex()? Could anyone > give me some examples? Thanks. > > Best, > John Lin > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas >
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