Python index a list where a regex matches

Question

Again recognizing that this is similar to a few other questions on SO but which I haven't been able to convert for my purposes. eg. with the snippet below

import re
a = ['rhubarb','plain custard','jam','vanilla custard','pie','cheesecake']
s = re.compile('custard')

I'd like to be able to get a list

[2,4]

which is the index of the two custard strings. I thought the question below would help but I haven't been able to figure out how to apply it here.

Python equivalent of which() in R

Are you sure you want [2,4] or do you want [1,3]? Indexes in python start at 0. So if you're looking to use those values to index into the original list, they will be wrong. — Jonathon Reinhart
– Jonathon Reinhart, Commented May 17, 2013 at 6:00

jamylak · Accepted Answer · 2013-05-17 06:38:00Z

11

>>> import re
>>> a = ['rhubarb','plain custard','jam','vanilla custard','pie','cheesecake']
>>> [i for i, s in enumerate(a, start=1) if re.search('custard', s)]
[2, 4]

note Python uses 0-index so I added the start=1 parameter to enumerate. In practice you should leave off start=1 to have the default start=0.

edited May 17, 2013 at 6:38

answered May 17, 2013 at 5:59

jamylak

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1 Comment

TerryA Over a year ago

Wow, I did not know about that extra parameter. +1

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