[Python-Dev] Emit SyntaxWarning on unrecognized backslash escapes?

[M.-A. Lemburg]

On 23.02.2015 23:50, Nick Coghlan wrote:
> On 24 February 2015 at 08:40, Nick Coghlan <ncoghlan at gmail.com> wrote:
>> On 24 February 2015 at 07:39, Mark Lawrence <breamoreboy at yahoo.co.uk> wrote:
>>> On 23/02/2015 21:27, Serhiy Storchaka wrote:
>>>>
>>>> On 23.02.15 21:58, Joao S. O. Bueno wrote:
>>>>>
>>>>> That happens all the time, and is this use case that should possibly
>>>>> be addressed here - maybe
>>>>> something as simple as adding a couple of paragraphs to different places
>>>>> in the documentation could mitigate the issue. (in contrast to make a
>>>>> tons of otherwise valid code
>>>>> to become deprecated in a couple releases).
>>>>
>>>>
>>>> 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.
>>>
>>> Isn't this why users have help desks?
>>
>> Most don't, and cases like "\n" or "\t" in a Windows path name being
>> converted to whitespace are utterly impossible to look up in an
>> internet search when they fail, so a user learning on their own gets
>> left with a broken program and no particularly effective ways to ask
>> for help figuring it out.

I think the easiest way would be to tweak the error message
output to indicate the real problem.

At the moment, you get:

>>> open('c:\test.txt')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: 'c:\test.txt'

which isn't helpful.

It would be better to display the escapes as what they are:

FileNotFoundError: [Errno 2] No such file or directory: 'c:      est.txt'

or use a special representation function to highlight the
possible problem:

FileNotFoundError: [Errno 2] No such file or directory: 'c:[\t]est.txt' - warning: embedded escapes

with the representation being:

"'c:[\t]est.txt' - warning: embedded escapes"

Such a change doesn't require a deprecation phase or a PEP.

-- 
Marc-Andre Lemburg
eGenix.com

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