test_re.py 文件源码

def test_lookbehind(self):
        self.assertTrue(re.match(r'ab(?<=b)c', 'abc'))
        self.assertIsNone(re.match(r'ab(?<=c)c', 'abc'))
        self.assertIsNone(re.match(r'ab(?<!b)c', 'abc'))
        self.assertTrue(re.match(r'ab(?<!c)c', 'abc'))
        # Group reference.
        with check_warnings(('', RuntimeWarning)):
            re.compile(r'(a)a(?<=\1)c')
        # Named group reference.
        with check_warnings(('', RuntimeWarning)):
            re.compile(r'(?P<g>a)a(?<=(?P=g))c')
        # Conditional group reference.
        with check_warnings(('', RuntimeWarning)):
            re.compile(r'(a)b(?<=(?(1)b|x))c')
        # Group used before defined.
        with check_warnings(('', RuntimeWarning)):
            re.compile(r'(a)b(?<=(?(2)b|x))(c)')