a simple regexp generator

regenerate.py

import re
from enum import Enum


class State(Enum):
    Initial = 0
    D = 10
    DRest = 11
    S = 20
    SRest = 21
    W = 30
    WRest = 31
    Other = 100


class ReGenerate(object):
    def __init__(self):
        self.tokens = []
        self.current_state: State.value = State.Initial
        self.fragment = ''

    def flush(self, ch: str):
        if self.fragment:
            self.tokens.append(self.fragment)
            self.fragment = ''

        if self.is_d(ch):
            self.fragment = r'\d'
            self.current_state = State.D
        elif self.is_w(ch):
            self.fragment = r'\w'
            self.current_state = State.W
        elif self.is_space(ch):
            self.fragment = r'\s'
            self.current_state = State.S
        else:
            self.fragment = re.escape(ch)
            self.current_state = State.Other

    def generate(self, data: str):
        for ch in data:
            if self.current_state == State.Initial:
                self.flush(ch)
            elif self.current_state == State.D:
                if self.is_d(ch):
                    self.current_state = State.DRest
                    self.fragment += r'+'
                else:
                    self.flush(ch)
            elif self.current_state == State.DRest:
                if not self.is_d(ch):
                    self.flush(ch)
            elif self.current_state == State.W:
                if self.is_w(ch):
                    self.current_state = State.WRest
                    self.fragment += r'+'
                else:
                    self.flush(ch)
            elif self.current_state == State.WRest:
                if not self.is_w(ch):
                    self.flush(ch)
            elif self.current_state == State.S:
                if self.is_space(ch):
                    self.current_state = State.SRest
                    self.fragment += r'+'
                else:
                    self.flush(ch)
            elif self.current_state == State.SRest:
                if not self.is_space(ch):
                    self.flush(ch)
            else:
                self.flush(ch)

        self.flush('')
        return ''.join(self.tokens)

    def is_d(self, ch: str):
        return re.match(r'[\d]', ch)

    def is_space(self, ch: str):
        return re.match(r'[\s]', ch)

    def is_w(self, ch: str):
        return re.match(r'[\w]', ch)


if __name__ == '__main__':
    # output: \w+\s\w+\s\w+\s\w+,\s\w'\w\s\d+\s\w+\s\w+
    regexp = ReGenerate().generate('My name is Bob, I\'m 25 years old')
    print(regexp)