regex.py 文件源码

def __and__(self, regex):
        """
        Create new optimized version of a & b.
        Returns None if there is no interesting optimization.

        >>> RegexEmpty() & RegexString('a')
        <RegexString 'a'>
        """
        if regex.__class__ == RegexEmpty:
            return self
        new_regex = self._and(regex)
        if new_regex:
            return new_regex
        else:
            return RegexAnd((self, regex))