test_re.py 文件源码

def test_string_boundaries(self):
        # See http://bugs.python.org/issue10713
        self.assertEqual(re.search(r"\b(abc)\b", "abc").group(1),
                         "abc")
        # There's a word boundary at the start of a string.
        self.assertTrue(re.match(r"\b", "abc"))
        # A non-empty string includes a non-boundary zero-length match.
        self.assertTrue(re.search(r"\B", "abc"))
        # There is no non-boundary match at the start of a string.
        self.assertFalse(re.match(r"\B", "abc"))
        # However, an empty string contains no word boundaries, and also no
        # non-boundaries.
        self.assertIsNone(re.search(r"\B", ""))
        # This one is questionable and different from the perlre behaviour,
        # but describes current behavior.
        self.assertIsNone(re.search(r"\b", ""))
        # A single word-character string has two boundaries, but no
        # non-boundary gaps.
        self.assertEqual(len(re.findall(r"\b", "a")), 2)
        self.assertEqual(len(re.findall(r"\B", "a")), 0)
        # If there are no words, there are no boundaries
        self.assertEqual(len(re.findall(r"\b", " ")), 0)
        self.assertEqual(len(re.findall(r"\b", "   ")), 0)
        # Can match around the whitespace.
        self.assertEqual(len(re.findall(r"\B", " ")), 2)