If you build a regular expression with bytes, patterns such as \d and \w only match ASCII characters; in contrast, if these patterns are given as str, they match Unicode digits or letters beyond ASCII.

Ramanujan.py

import re
re_numbers_str = re.compile(r'\d+') 
re_words_str = re.compile(r'\w+')
re_numbers_bytes = re.compile(rb'\d+') 
re_words_bytes = re.compile(rb'\w+')
text_str = ("Ramanujan saw \u0be7\u0bed\u0be8\u0bef" 
 " as 1729 = 1³ + 12³ = 9³ + 10³.") 
text_bytes = text_str.encode('utf_8') 
print('Text', repr(text_str), sep='\n ')
print('Numbers')
print(' str :', re_numbers_str.findall(text_str)) 
print(' bytes:', re_numbers_bytes.findall(text_bytes)) 
print('Words')
print(' str :', re_words_str.findall(text_str)) 
print(' bytes:', re_words_bytes.findall(text_bytes))