re(regex) should take '\0' as '\g<0>' instead of '\x00'

[noisnemid]

Feature or enhancement

CURRENT STATUS

Python 3.13.1 (tags/v3.13.1:0671451, Dec  3 2024, 19:06:28) [MSC v.1942 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import re
>>> p=re.compile(r'a')

p.sub(r'\0-','axa')
'\x00-x\x00-'

 p.sub(r'\g<0>-','axa')
'a-xa-'

Reasons for this

The consistency of Python code style is an important reason for its favorable reception. However, as shown in the code demonstrated just now, this is not well achieved in the re module. \1 and the like are treated as capture groups, but \0 is the only exception, which is unreasonable.

[skirpichev]

but \0 is the only exception

It's not. \111 is another "exception", for example.

Could you please be more precise, which meaning you suggest for \0? Anyway, it will be a huge compatibility break and also introduce incompatibility with perl regular expressions.

This is something that should be discussed first on https://discuss.python.org/c/ideas/6

[noisnemid]

Indeed, it should be discussed first( or just pending...).
Generally, \0 refers to the default capture group, $0 .

I thought in string find/replace operations, a group catching is more frequently used than '\x00'.

[picnixz]

The docs say (emphasis mine):

\number
matches the contents of the group of the same number. Groups are numbered starting from 1. For example, (.+) \1 matches 'the the' or '55 55', but not 'thethe' (note the space after the group). This special sequence can only be used to match one of the first 99 groups. If the first digit of number is 0, or number is 3 octal digits long, it will not be interpreted as a group match, but as the character with octal value number. Inside the '[' and ']' of a character class, all numeric escapes are treated as characters.

So this is not an issue IMO.

[skirpichev]

Indeed, it should be discussed first

So, closing for now.