r'\U' gives SyntaxError: (unicode error) 'rawunicodeescape' codec can't decode bytes

Question

I'm in Python 2.7.

test = r'\U'

gives:

SyntaxError: (unicode error) 'rawunicodeescape' codec can't decode bytes in position 0-1: truncated \uXXXX

I thought raw strings were supposed to ignore backslashes. No?

I want a string that actually contains '\' and 'U'.

In case it matters, I'm also using:

from __future__ import (absolute_import, division, print_function, unicode_literals)

If I knew that I would have answered instead of upvoting. Hopefully someone who knows these things will wander by and enlighten us. — Stephen Rauch, Mar 29 '18 at 02:18
Weird. This problem disappears when I remove the `unicode_literals` import. And of course, I can do this in Python 3 no problems. — juanpa.arrivillaga, Mar 29 '18 at 02:19
@juanpa.arrivillaga I don't consider this a duplicate. That other question doesn't address the raw string issue. (The answer does, but not the question.) — nerdfever.com, Mar 29 '18 at 13:13

score 3 · Accepted Answer · answered Mar 29 '18 at 02:19

Python 2 raw unicode strings have a bizarre quirk where they still process \u and \U sequences:

When an 'r' or 'R' prefix is used in conjunction with a 'u' or 'U' prefix, then the \uXXXX and \UXXXXXXXX escape sequences are processed while all other backslashes are left in the string.

The docs describe the behavior of combining the r and u prefixes, but I believe this also applies to combining the r prefix and unicode_literals.

r'\U' gives SyntaxError: (unicode error) 'rawunicodeescape' codec can't decode bytes

1 Answers1