Add space before a substring in a string using regex in python

Question

I have two lists:

list_1 = ["TP", "MP"]

list_2 = ["This is ABC12378TP0892S3", "This is XYZ12378MP0892S3"]

I want take elements from list_1 and search in strings of list_2. If found (for example TP is present in list_2's first string, MP is present in list_2's second string), remove what is to the right of TP, MP etc. and insert space to left of it.

I tried the below with re, but it is removing only the right part:

[ re.sub(r'(' +  '|'.join(list_1) + ')\d+', r'\1', string) for string in list_2 ]

Martin Evans · Accepted Answer · 2016-11-22 10:57:52Z

1

You could compile a regular expression as follows, and then use it to do a sub() on each list entry:

import re

list_1 = ["TP", "MP"]
list_2 = ["This is ABC12378TP0892S3", "This is XYZ12378MP0892S3", "SDTP This is ABC12378TP0892S3"]    

re_sub = re.compile(r'(.*\b\w+)({}).*'.format('|'.join(list_1))).sub
list_2 = [re_sub(r'\1 \2', t) for t in list_2]

print list_2

This would display:

['This is ABC12378 TP', 'This is XYZ12378 MP', 'SDTP This is ABC12378 TP']

In this example, the search pattern being used is:

(.*\b\w+)(TP|MP).*

edited Nov 22, 2016 at 10:57

answered Nov 22, 2016 at 10:48

Martin Evans

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2 Comments

Salman Baqri Over a year ago

Could please explain this [re_sub(r'\1 \2', t) for t in list_2]. How exactly it is working?

Martin Evans Over a year ago

The search pattern has two sets of (....). When using sub(), the \1 means to substitute the current location with the contents of the first (), and \2, the contents of the second ().

OneCricketeer · Accepted Answer · 2016-11-22 05:21:10Z

0

I think you were close. Add the space... r' \1'

Not sure about \d+, either, so replace that with .*

>>> [ re.sub(r'(' +  '|'.join(list_1) + ').*', r' \1', string) for string in list_2 ]
['This is ABC12378 TP', 'This is XYZ12378 MP']

answered Nov 22, 2016 at 5:21

OneCricketeer

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6 Comments

Salman Baqri Over a year ago

@cricket-007 What if I have two substrings and I only want to insert space in one.Example list_1 = ["TP", "MP"] list_2 = ["SDTP This is ABC12378TP0892S3", "This is XYZ12378MP0892S3"] and I don"t want to insert space for SDTP.

OneCricketeer Over a year ago

If that was your question, then you should have asked that from the start... You can't do the list comprehension, then, because you would need ' \2' instead of ' \1'

Salman Baqri Over a year ago

@cricket-007 SDTP can occur anywhere in the string. Could you please elaborate ?

OneCricketeer Over a year ago

Sure, but for the regex replacement, order matters... "SDTP This is ABC12378TP", there are two. If you want the space on the "ABC12378TP" part, then you have to do more work (or it just isn't possible)

Salman Baqri Over a year ago

@cricket-007 Is there anyway to use Quantifiers for this? Or if it is fixed SDTP occurs as first position in the string then?

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