Sword finger offer (52): regularization expression

Too many considerations , I don't understand yet , Put the code on first ！

class Solution:
    # s, pattern All strings 
    def match(self, s, pattern):
        # write code here
        if len(s) == 0 and len(pattern) == 0:
            return True
        elif len(s) != 0 and len(pattern) == 0:
            return False
        elif len(s) == 0 and len(pattern) != 0:
            if len(pattern) > 1 and pattern != 0:
                return self.match(s,pattern[2:])
            else:
                return False
        else:
            if len(pattern) > 1 and pattern[1] == '*':
                if s[0] != pattern[0] and pattern[0] != '.':
                    return self.match(s,pattern[2:])
                else:
                    return self.match(s,pattern[2:]) or self.match(s[1:],pattern[2:]) or self.match(s[1:],pattern)
            else:
                if s[0] == pattern[0] or pattern[0] == '.':
                    return self.match(s[1:],pattern[1:])
                else:
                    return False