On 01/24/2014 07:36 PM, Andrew Barnert wrote:
While we're speculatively overgeneralizing, couldn't all of the index/find/remove/replace/etc. methods take a negative n to count from the end, making r variants unnecessary?
Strings already provide rfind and rindex (they're just not part of the general sequence API). Since strings are immutable, there's also no call for an "remove".
I was responding to Serhiy's (probably facetious or devil's advocate) suggestion that we should regularize the API: add rfind and rindex to tuple (and presumably Sequence), and those plus rremove to list (and presumably MutableSequence), and so on.
My point was that if we're going to be that radical, we might as well consider removing methods instead of adding them. Some of the find-like methods already take negative indices; expanding that to all of the index-based methods, and doing the equivalent to the count-based ones, and adding a count or index to those that have neither, would mean all of the "r" variants could go away.
How about a keyword to specify which end to index from? When used, it would disable negative indexing as well. When not used the current behaviour with negative indexing would be the default.
direction=0 # The default with the current (or not specified) # negative indexing allowed.
direction=1 # From first. Negative indexing disallowed. direction=-1 # From last. Negative indexing disallowed.
(A shorter key word would be nice, but I can't think of any that is as clear.)
The reason for turning off the negative indexing is it would also offer a way to avoid some indexing bugs as well. (Using negative indexing with a reversed index is just asking for trouble I think.)
While the spelling isn't a short and concise as I would like, I could always wrap them in short helper functions if I wanted... ffind, rfind, findex, rindex.. etc. But those wouldn't need to be added to python.
I think it's pretty obvious that both this suggestion and Serhiy's are not worth doing for Python—the language has had pretty much the same set of find-style methods for decades, most of them are used frequently, and people rarely go looking for any of the "missing" ones, so why change it? (And I think that was Serhiy's point as well, but I don't want to speak for him.) If people_do_ find themselves missing one particular variant, just adding that one more variant is a lot more conservative than changing everything; if not, there's no reason to add anything at all.