Python regex replace part of string in a column which occurs after specific regex

Question

I want to remove occurrence V, I or VI only when it is inside a bracket such as below:

Input:

VINE(PCI); BLUE(PI)
BLACK(CVI)
CINE(PCVI)

Output desired:

VINE(PC); BLUE(P)
BLACK(C)
CINE(PC)

When I use df['col'].str.replace('[PC]+([VI]+)', "") it replaces everything inside the brackets. and when I use just df['col'].str.replace('[VI]+', "") it ofcourse doesn't work as it then removes all other occurrences of V and I. Inside the bracket there will only be these 4 letters in any combination of either (or both) PC and either (or both) VI. What am I doing wrong here pls?

Thanks

I have used pythex.org and it shows that the match capture should be as I want, but the match is the whole bit inside the string — spiff
– spiff, Commented Nov 7, 2018 at 3:23

cs95 · Accepted Answer · 2018-11-07 03:40:02Z

1

Use str.replace with a capture group and callback:

import re
df['col'] = df['col'].str.replace(
    r'\((.*?)\)', lambda x: re.sub('[VI]', '', f'({x.group(1)})'))

Or,

df['col'] = df['col'].str.replace(r'\((P|PC|C)[VI]+\)',r'(\1)') # Credit, OP
print(df)
                 col
0  VINE(PC); BLUE(P)
1           BLACK(C)
2           CINE(PC)

edited Nov 7, 2018 at 3:40

answered Nov 7, 2018 at 3:29

cs95

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4 Comments

spiff Over a year ago

actually V will be treated the same way as I.. so will adjust for that too.. but I see what you are doing.. just going tom implement and come back

spiff Over a year ago

great! used this df['col'].str.replace(r'\((P|PC|C)[VI]+\)',r'(\1)', regex=True) and it works. Will accept the answer and read and learn the other ways. I actually have a case such as CASH(PVI;CVI) which is odd, as it should just have been (PCVI) .. so will make adjustments for that

spiff Over a year ago

thank you! What does f'() do? as in 'f' and not 'r' or anything else

cs95 Over a year ago

@spiff f-strings are python3.6 syntax meant to perform string formatting. Also, wanted to mention the first solution can be easily extended to remove other characters besides V and I later if needed.

Neroksi · Accepted Answer · 2018-11-07 04:43:19Z

0

Another solution using only pandas :

import pandas as pd
S = pd.Series(["VINE(PCI)", "BLUE(PI)", "BLACK(CVI)", 'CINE(PCVI)'])
S.str.split('[\(\)]').apply(lambda x :  x[0] + "(" + x[1].replace("I", "").replace("V", "") + ")" + x[2])
0    VINE(PC)
1     BLUE(P)
2    BLACK(C)
3    CINE(PC)
dtype: object

answered Nov 7, 2018 at 4:43

Neroksi

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