Regular expression in python with variable strings

Question

I have the foll. strings in python:

Vladimir_SW_crop_mask_ERA.hdr
Ust_Ordynskiy_Buryatskiy_AO_SW_crop_mask_ERA.hdr
Ingush_WW_crop_mask.dat

I want to parse these strings such that:

Get the crop type which can be either SW or WW
Get the region name which is the text preceding _SW or _WW

I was doing str.split('_')[0] to get region name, but that fails in case of Ust_Ordynskiy_Buryatskiy_AO_SW_crop_mask_ERA.hdr, where the region name is Ust_Ordynskiy_Buryatskiy_AO

thanks @Jasper, it is a bad name for the question :) but 'regular expression in python' was already asked — user308827
– user308827, Commented Nov 11, 2015 at 19:50

ekhumoro · Accepted Answer · 2015-11-11 19:55:30Z

2

You can partition and rpartition to do this:

>>> s = 'Vladimir_SW_crop_mask_ERA.hdr'
>>> s.partition('_crop')[0].rpartition('_')[::2]
('Vladimir', 'SW')
>>> s = 'Ust_Ordynskiy_Buryatskiy_AO_SW_crop_mask_ERA.hdr'
>>> s.partition('_crop')[0].rpartition('_')[::2]
('Ust_Ordynskiy_Buryatskiy_AO', 'SW')

answered Nov 11, 2015 at 19:55

ekhumoro

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Jasper · Accepted Answer · 2015-11-11 19:55:05Z

1

The following regexp should work:

(.*)_(SW|WW)

Match everything up to an underscore followed by either SW or WW and put this in the first matching group and the following SW or WW in the second group:

import re

strs = ["Vladimir_SW_crop_mask_ERA.hdr",
        "Ust_Ordynskiy_Buryatskiy_AO_SW_crop_mask_ERA.hdr",
        "Ingush_WW_crop_mask.dat"]

for s in strs:
    print(re.match("(.*)_(SW|WW)", s).groups())

Result:

('Vladimir', 'SW')
('Ust_Ordynskiy_Buryatskiy_AO', 'SW')
('Ingush', 'WW')

answered Nov 11, 2015 at 19:55

Jasper

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