"""Optional fixer that changes all unprefixed string literals "..." to b"...". br'abcd' is a SyntaxError on Python 2 but valid on Python 3. ur'abcd' is a SyntaxError on Python 3 but valid on Python 2. """ from __future__ import unicode_literals import re from lib2to3.pgen2 import token from lib2to3 import fixer_base _literal_re = re.compile(r"[^bBuUrR]?[\'\"]") class FixBytes(fixer_base.BaseFix): BM_compatible = True PATTERN = "STRING" def transform(self, node, results): if node.type == token.STRING: if _literal_re.match(node.value): new = node.clone() new.value = u'b' + new.value return new