This is a String Calculator

string_calculator_kata.py

import re

def add(text):
    """
    String Calculator
    http://osherove.com/tdd-kata-1/
    """
    if not text:
        return 0

    text = text.split('\n')
    total = 0

    pattern = None

    for line in text:
        if not pattern:
            if line.startswith('//'):
                delimeters_cst = [e[1:-1] for e in re.findall(r'\[.+?\]', line)]
                if not delimeters_cst:
                    delimeters_cst = [line[2:]]

                delimeters = delimeters_cst
                skip_line = True
            else:
                delimeters = [',']
                skip_line = False

            delimeters = [re.escape(e) for e in delimeters]
            pattern = '|'.join([e for e in delimeters])

            if skip_line:
                continue

        numbers = re.split(pattern, line)

        for number in numbers:
            number_int = int(number)
            if number_int < 1000:
                total += number_int
    
    return total