i have regex https://regex101.com/r/2H5ew6/1

(\!|\@)(1) 

Hello!1 World

and i wanna get first mark (!|@) and change the number 1 to another number 2 I did

{\1}2_
\1\\2_

but it adds extra text and i just wanna change the number

i expect result to be

Hello!2_World

and ifusing @ to be

Hello@2_World

CodePudding user response：

Match and capture either ! or @ in a named capture group, here called char, if followed by one or more digits and a whitespace:

(?P<char>[!@])\d \s

Substitute with the named capture, \g<char> followed by 2_:

\g<char>2_

Demo

If you only want the substitution if there's a 1 following either ! or @, replace \d with 1.

CodePudding user response：

In your substitution you need to change the {\1}2_ to just 2_.

string = "Hello!1 World"
pattern = "(\!|\@)(1)"
replacement = "2_"
result = re.sub(pattern, replacement, string)

CodePudding user response：

Why not: string.replace('!1 ', '!2_').replace('@1 ', '@2_') ?

>>> string = "Hello!1 World"
>>> repl = lambda s: s.replace('!1 ', '!2_').replace('@1 ', '@2_')
>>> string2 = repl(string)
>>> string2
'Hello!2_World'
>>> string = "Hello!12 World"
>>> string2 = repl(string)
>>> string2
'Hello!12 World'