Extract element within string into nested list

Question

I am working on a routing project. The route looks like this "CNSHG(B)-PAMIT(R)-COCTG(B)-USHOU(R)-COCTG(B)-USMSY" and I want to break it into a nested list. Also, a route contains multiple segments for example CNSHG-PAMIT is one segment transported using B and then PAMIT-COCTG transported using R i.e, Rail, and so on.

Input:

"CNSHG(B)-PAMIT(R)-COCTG(B)-USHOU(R)-COCTG(B)-USMSY"

The output should be like this:

[[CNSHG, PAMIT, B],[PAMIT, COCTG, R],[COCTG, USHOU, B],[USHOU, COCTG, R],[COCTG, USMSY, B]]

I have tried using regex and the below codes but it didn't work.

route.str.extract('(.)\s\((.\d+)')

Thanks a lot.

Why are you using (.\d+)? There are no digits in your input. — MattDMo
– MattDMo, Commented Dec 23, 2021 at 13:15
Also, your final destination USMSY doesn't have a means of transportation following it (B, R, or something else). Will that always be the case? — MattDMo
– MattDMo, Commented Dec 23, 2021 at 13:20
@MattDMo The transport mode is written in brackets with the first transport port, so there is no mode on the last port because that is the destination. — freak7
– freak7, Commented Dec 23, 2021 at 13:24

Wiktor Stribiżew · Accepted Answer · 2021-12-23 13:23:20Z

2

You can use

import pandas as pd
df = pd.DataFrame({'col':["CNSHG(B)-PAMIT(R)-COCTG(B)-USHOU(R)-COCTG(B)-USMSY"]})
df['result'] = df['col'].str.findall(r'(\w+)\((?=[^()]*\)-(\w+))([^()]*)\)')

Output of df['result']:

[('CNSHG', 'PAMIT', 'B'), ('PAMIT', 'COCTG', 'R'), ('COCTG', 'USHOU', 'B'), ('USHOU', 'COCTG', 'R'), ('COCTG', 'USMSY', 'B')]

See the regex demo. Details:

(\w+) - one or more word chars
\( - a ( char
(?=[^()]*\)-(\w+)) - a positive lookahead that requires (immediately to the right of the current location):
- [^()]* - zero or more chars other than ( and )
- \)- - a )- string
- (\w+) - Group 2: one or more word chars
([^()]*) - Group 3: zero or more chars other than ( and )
\) - a ) char.

answered Dec 23, 2021 at 13:23

Wiktor Stribiżew

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