[Python-Dev] \u and \U escapes in raw unicode string literals (original) (raw)

Guido van Rossum guido at python.org
Fri May 11 00:11:37 CEST 2007

On 5/10/07, M.-A. Lemburg <mal at egenix.com> wrote:

On 2007-05-10 20:53, Paul Moore wrote: > On 10/05/07, Guido van Rossum <guido at python.org> wrote: >> I just discovered that, in all versions of Python as far back as I >> have access to (2.0), \uXXXX escapes are interpreted inside raw >> unicode strings. Thus: > [...] >> Does anyone remember why it is done this way? The reference manual >> describes this behavior, but doesn't give an explanation: > > My memory is so dim as to be more speculation than anything else, but > I suspect it's simply because there's no other way of including > characters outside the ASCII range in a raw string.

This is per design (see PEP 100) and was done for the reason given by Paul. The motivation for the chosen approach was to make Python's raw Unicode strings compatible to Java's raw Unicode strings: http://java.sun.com/docs/books/jls/secondedition/html/lexical.doc.html

I'm not sure what Java compatibility buys us. It is also far from perfect -- IIUC, in Java if you write \u0022 (that's the " character) it counts as an opening or closing quote, and if you write \u005c (a backslash) it can be used to escape the following character. OTOH, in Python, you can write ur"C:\Program Files\u005c" and voila, a raw string terminating in a backslash. (In Java this would escape the " instead.)

However, I understand the other reason (inclusion of non-ASCII characters in raw strings) and I reluctantly agree with it. Reluctantly, because it means I can't create a raw string containing a \ followed by u or U -- I needed one of those today.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

More information about the Python-Dev mailing list