Python regex replace digit -1

Question

I am trying to convert a String into proper JSON notation. This string, got some correct indexes (with [idx]), and some incorrect indexes (with dot notation .idx. with these last ones starting by 1, instead of by 0). Is there anyway to "handle" captured groups using python re library or similar?

This is what I have:

import re

a = "a.[0].b.1.c"
re.sub(r'\.(\d)\.', r'.[\1].', a)  # Which provides: 'a.[0].b.[1].c'

I would like it to give me 'a.[0].b.[0].c', but I do not know how can I perform operations on the captured group $1. Is it possible?

This? Not sure if transferable... unix.stackexchange.com/questions/278300/… — mcsoini
– mcsoini, Commented Apr 12, 2021 at 6:58

Mustafa Aydın · Accepted Answer · 2021-04-12 07:05:11Z

2

The replacer argument of re.sub can be a function and that function gets passed the match object upon which you can perform operations:

def replacer(mo):
    captured_group = mo.group(1)
    one_subtracted = str(int(captured_group) - 1)
    to_replace = ".[" + one_subtracted + "]."
    return to_replace

and using:

>>> re.sub(r"\.(\d)\.", replacer, a)
'a.[0].b.[0].c'

Note that mo includes all the to-be-replaced string that your pattern matches, so we put the matched .s back.

If you want a lambda:

re.sub(r"\.(\d)\.", lambda mo: ".[" + str(int(mo.group(1))-1) + "].", a)

edited Apr 12, 2021 at 7:05

answered Apr 12, 2021 at 7:01

Mustafa Aydın

18.4k4 gold badges21 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Mayday Over a year ago

You just missed to add the square brackets. Would be ".[" + ... + "].". Appart from that, ir works like a charm! Thank you very much!!!

Mustafa Aydın Over a year ago

@Mayday Yeah, i was editing that :) Glad to be of help!

Collectives™ on Stack Overflow

Python regex replace digit -1

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related