search sub-string from backward using Python

Question

Wondering if there is a neat API in Python to search a string from backward (from a specific position in a string), for example, in string "Hello StackOverflow Hello Python", suppose I want to find the index of sub-string "Hello" which is previous to sub-string "Python"?

thanks in advance, Lin

Downvoted. First result for "python string" search gives you docs.python.org/2/library/string.html#string.rfind — viraptor
– viraptor, Commented Feb 27, 2016 at 1:29
@viraptor, nice catch. I am confused by rindex and rfind, which one is for my problem? Thanks. — Lin Ma
– Lin Ma, Commented Feb 27, 2016 at 1:45
Either one. The question is - do you want an exception thrown (rindex) or -1 returned (rfind) if the strings are missing. — viraptor
– viraptor, Commented Feb 27, 2016 at 1:49
@viraptor, I just need to get -1 when there is no hit, whether Exception is returned or not is not important, your recommendations are highly appreciated. :) — Lin Ma
– Lin Ma, Commented Feb 27, 2016 at 1:55

aghast · Accepted Answer · 2016-02-27 01:29:50Z

3

Yes, it's called str.rindex(). It takes arguments sub - a substring to look for, start - a starting position, and end.

It is the reverse of the index function. There are some others, like rsplit, too.

answered Feb 27, 2016 at 1:29

aghast

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4 Comments

Lin Ma Over a year ago

Thanks Austin, always good to learn from you. Just to clarify, do you mean using rindex or using rfind? :)

aghast Over a year ago

That's up to you. Do you want a ValueError? But for your information, the index and rindex functions appear in a lot of languages, so they're a good pair to remember.

Lin Ma Over a year ago

Hi Austin, I just need to get -1 when there is no hit, whether ValueError is returned or not is not important, your recommendations are highly appreciated. :)

Lin Ma Over a year ago

Thanks for all the help, Austin. Mark your reply as answered.

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