Python 2.6: false positive W605 invalid escape sequence

[jwilk]

I'm getting this false positive:

$ echo 'br"\s"' | python2.6 -m pycodestyle /dev/stdin
/dev/stdin:1:3: W605 invalid escape sequence '\s'

I suspect this is caused by Python issue #15054.

You may want to disable W605 for Python 2.6.

[sigmavirus24]

I don't think our checks are specific to Python versions. That said, I think the error message could be improved. And a PR to clarify what's "invalid" about it (for Python 3.7) is needed. That would allow folks to --ignore W605 if they never plan to use Python 3.7

[seeeturtle]

@sigmavirus24, afaik, the warning is changed since python 3.6
(Note https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals)
isn't it?

[sigmavirus24]

I'm sorry @seeeturtle, could you rephrase? I'm having trouble understanding your question.

[seeeturtle]

Sorry for too short explanation

Changed in version 3.6: Unrecognized escape sequences produce a DeprecationWarning. In some future version of Python they will be a SyntaxError.

https://bugs.python.org/issue27364

https://docs.python.org/3.6/whatsnew/3.6.html#deprecated-python-behavior

Based on the above three, I thought that the patch of rasing DeprecationWarning for invalid escape sequence is changed since python 3.6.
However, your comment seems to mean to ignore python under 3.7 not 3.6.

Am I talking right?

@sigmavirus24

[sigmavirus24]

Oh sorry, I think my earlier comments were too short too 😃 Thanks for explaining what you were saying.

So, the warning was introduced in 3.6 but those escape sequences aren't invalid yet. I think we added the check because the invalid syntax error was going to be introduced in 3.7. Also, while discussing misunderstandings: I misunderstood what @jwilk was suggesting was the problem here. The problem here is how python 2.6 tokenizes bytestrings. I think we can fix that easily Sorry for the confusion.

[seeeturtle]

No problem :)
Btw, maybe I can send PR for modifying docs about w605 to show that it will not gonna produce error until python 3.7.

[sigmavirus24]

@seeeturtle absolutely!

[seeeturtle]

@sigmavirus24, it seems W605 will be changed into Error starting with Python 3.8 not Python 3.7 since it breaks a lot of code.

Note:

• https://bugs.python.org/issue27364#msg269372
• https://bugs.python.org/issue27364#msg269376

btw, where can i add some notes for certain warning in docs?

[gdevenyi]

This also triggers a false positive for lines defining a regex:

import re
re.match("^([-+]?\d+|^\d+%)$", string)

W605 invalid escape sequence '\d'

[FichteFoll]

@gdevenyi this is intended as you should be using a raw strings for regular expressions in most cases. \d is an invalid string escape sequence.

[gdevenyi]

Hrm, okay, it works with a raw string.

[serhiy-storchaka]

br"\s" doesn't contain an invalid escape sequence because it is a raw string.

The sequence \s is considered invalid only in non-raw strings.