[issue28611] Syntax error when using raw strings ending with a backslash.

[Ned Deily]

Ned Deily added the comment:

To expand a bit, the "Python Language Reference" section on "String and Byte 
Literals" explains:

"Even in a raw literal, quotes can be escaped with a backslash, but the 
backslash remains in the result; for example, r"\"" is a valid string literal 
consisting of two characters: a backslash and a double quote; r"\" is not a 
valid string literal (even a raw string cannot end in an odd number of 
backslashes). Specifically, a raw literal cannot end in a single backslash 
(since the backslash would escape the following quote character). Note also 
that a single backslash followed by a newline is interpreted as those two 
characters as part of the literal, not as a line continuation."

https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals

Because of the difference between Posix- and Windows-style paths and the 
potential conflicts in the use of `\` (such as you ran into), Python provides 
the older os.path and the newer pathlib modules, both of which allow you to 
deal with path manipulations in a more platform-independent manner.

https://docs.python.org/dev/library/pathlib.html
https://docs.python.org/dev/library/os.path.html

--
nosy: +ned.deily

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[issue28611] Syntax error when using raw strings ending with a backslash.

[Emanuel Barry]

Emanuel Barry added the comment:

That's how strings work, unfortunately. You can't end any string (raw or not) 
with an odd number of backslashes. You could do the following to get around 
this limitation:

>>> r"C:\Folder" "\\"
'C:\\Folder\\'

As a side note, please don't upload screenshots if what you're capturing 
consists only of text (you can paste it directly in your message). This makes 
it impossible to copy-paste input in the interpreter to try to replicate the 
issue, and makes it harder/impossible for the blind and visually-impaired to 
contribute. Thanks!

--
nosy: +ebarry
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed
type: compile error -> behavior

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[issue28611] Syntax error when using raw strings ending with a backslash.

[Mallow]

New submission from Mallow:

I'm not sure if this is a bug or not but I've noticed a behavior that seems 
incorrect.

The use of raw strings, when used for directory paths ending with a back slash 
(/) creates a syntax error.

How to reproduce


Code:

print (r"C:\path\to\a\dir\" + "file.ext")

Result: Syntax Error

Why is this an error, (in my perspective)
-

One could attempt to be storing the directory information in a variable to 
write to file that is composed later but would be forced to use a cumbersome 
normal string having to escape all backslashes.

Example:

outputdir = r"C:\path\to\dir\"
filename = r"file.ext"
writetofile(outputdir + filename)

Argument for why the workaround is not a fix


I believe I read somewhere that python is smart enough to deal with filepaths 
correctly on linux and windows if you were to switch the slashes. So 
technically 
outputdir = r"C:/path/to/dir/" 
would work
however this is hard on the workflow since I find it easier to copy and paste 
paths within windows.

I guess it wouldn't be too unreasonable to do something like:
r"C:\path\to\dir/"

--
files: Capture.PNG
messages: 280057
nosy: princemallow
priority: normal
severity: normal
status: open
title: Syntax error when using raw strings ending with a backslash.
type: compile error
versions: Python 3.5
Added file: http://bugs.python.org/file45352/Capture.PNG

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