[Python-Dev] Emit SyntaxWarning on unrecognized backslash escapes? (original) (raw)

Chris Angelico rosuav at gmail.com
Tue Feb 24 08:02:03 CET 2015

On Tue, Feb 24, 2015 at 8:39 AM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Serhiy Storchaka wrote:

The problem is that the user don't know that he should read the documentation. It just find that his script works with "C:\sample.txt", but doesn't work with "D:\test.txt". He has no ideas what happen. Even with the syntax error, there are filenames that will mysteriously fail, e.g. "C:\ninjamoves.txt".

Yes, there are; but they will fail, rather than randomly happening to work. With the proposed syntax warning, there will be no cases which silently succeed; everything will either be interpreted as an escape sequence (as in your example), fail with a hard error ("C:\Users" in a Unicode string, or "C:\x-do-not-track"), or produce a warning (everything else). The most tricky escape sequence that I can envision is \134, so you might find that an all-numeric path gets beheaded:

print("C:\134689") C:\689

The chances that someone will accidentally get something like this are very low, and the main thing is, "\X" for any X will never be interpreted the same way as "\X", so the backslash will always be seen as special.

ChrisA

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