How to remake this python regex produces needed result

I need to remake regex so that it produces needed result

import re

txt = 'aba accca azzza wwwwa accca wwasdwaww abmasedmwa'

regex = re.sub(r'\ba([^a]+)a\b', r'!\1!', txt)
print(regex)

Output:

!b! !ccc! !zzz! wwwwa !ccc! wwasdwaww abmasedmwa

Needed output:

a!a a!!!a a!!!a wwwwa a!!!a wwasdwaww abmasedmwa

>Solution :

You can use

import re

txt = 'aba accca azzza wwwwa accca wwasdwaww abmasedmwa'
pattern = r'(?<=\ba)[^\Wa]+(?=a\b)'
print( re.sub(pattern, lambda x: '!' * len(x.group()), txt) )

See the Python demo.

Details

• (?<=\ba) – a positive lookbehind that matches a location that is immediately preceded with a at the start of a word
• [^\Wa]+ – one or more word chars other than a
• (?=a\b) – a positive lookahead that matches a location that is immediately followed with a at the end of a word

Output:

a!a a!!!a a!!!a wwwwa a!!!a wwasdwaww abmasedmwa

The lambda x: '!' * len(x.group()) replacement replaces the match value with the same amount of ! chars.