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examples/regex/duplicate_numbers.py

import re

text = "This is 1 string with 3 numbers: 34"

new_text = re.sub(r'(\d+)', r'\1\1', text)
print(new_text)   # This is 11 string with 33 numbers: 3434

double_numbers = re.sub(r'(\d+)', lambda match: str(2 * int(match.group(0))), text)
print(double_numbers)  # This is 2 string with 6 numbers: 68


# The same but in a function

def double(match):
    matched_number_as_str = match.group(0)
    number = int(matched_number_as_str)
    doubled_number = 2 * number
    doubled_number_as_str = str(doubled_number)
    return doubled_number_as_str

double_numbers = re.sub(r'(\d+)', double, text)
print(double_numbers)  # This is 2 string with 6 numbers: 68