bpo-11479: Added a discussion of trailing backslash in raw string to tutorial

[dancinglightning]

https://bugs.python.org/issue11479

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[Julian]

Personally I wouldn't mention this one -- it adds a runtime cost if it's inside some loop or function call, which on its own isn't a huge deal, but it also means you get unexpected behavior if you don't fully realize what this does and try it on r' foo bar \ baz quux\ .

I'd personally leave things with the last workaround (and not mention there are multiple), but if another workaround is desired, using two string literals with the terminal slash in a second one implicitly concatenated is the next-best-one to me:

fn = r'C:\this\will\work' '\\'

[dancinglightning]

Yeah, I do agree it adds to the runtime but I am pretty sure that this piece of information can be invaluable and many times go unnoticed. I too faced difficulty in comprehending the issue when I got stuck with it. I was able to resolve it later by reading various discussions.