🔒 🔒 Python Find and Replace using Backreference and Variable

[frigid kernel]

Please help on the below to get mentioned output using "re.sub"

import re year = '2025' source = '<publicationyear first=""/>' source = re.sub(r"(<publicationyear first=\")(\"/>)", fr"\1{year}\2", source) print(source)

Needed output: <publicationyear first="2025"/>

Tried in many sites but didn't get solutions with the combination of backreference and variable replacement.

[glad moth]

@frigid kernel

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[paper dew]

The issue is that your f-string turns into "\12025\2", which then gets interpreted by re.sub as \120 25 \2. With re, \xxx is interpreted as the octal number of a character, and oct(ord("P")) is indeed 0o120.

re.sub is the wrong tool for this, however if you have to use it because this is some sort of question/assignment, you can fix the regex engine being confused by using the long form for group references in substitution strings: rf"\g<1>{year}\g<2>"

The way I would recommended doing this, assuming source is static, is by f"{source[:24]}{year}{source[24:]}"

Also minor nitpick, but you should use rf instead of fr, since it is read as "raw f-string".

[frigid kernel]

please tell me what is the meaning of "[:24]"

[paper dew]

It's a slice. Normal indexing is [index], but adding a : does [start:end]. Omitting either start or end assumes you want the slice to continue all the way, so [:24] is saying "give me the substring from the start to index 23", and [24:] is saying "give me the substring from index 24 to the end.

>>> source = '<publicationyear first=""/>'
>>> print(source[:24])
<publicationyear first="
>>> print(source[24:])
"/>

[frigid kernel]

Than you so much. Very well explained. helped a lot.
Thanks friend.

[glad moth]

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🔒 Python Find and Replace using Backreference and Variable

[glad moth]

Python help channel closed

This help channel has been closed and it's no longer possible to send messages here. If your question wasn't answered, feel free to create a new post in #1035199133436354600. To maximize your chances of getting a response, check out this guide on asking good questions.