Why Can't Python'S Raw String Literals End With a Single Backslash

Why can't Python's raw string literals end with a single backslash?

The reason is explained in the part of that section which I highlighted in bold:

String quotes can be escaped with a
backslash, but the backslash remains
in the string; 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 string 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 string, not as a line
continuation.

So raw strings are not 100% raw, there is still some rudimentary backslash-processing.

how to create a raw string when it's last character is a `\` in python

You can concat another normal string:

>>> r'\abc\test' + '\\'
'\\abc\\test\\'

Why can't I end a raw string with a backslash?

You still need \ to escape ' or " in raw strings, since otherwise the python interpreter doesn't know where the string stops. In your example, you're escaping the closing '.

Otherwise:

r'it wouldn\'t be possible to store this string'
r'since it'd produce a syntax error without the escape'

Look at the syntax highlighting to see what I mean.

Python: Why do raw strings require backslash to be escaped?

because '\' has special meaning in re it means escape the character after it in the language you use to define a re so if you want to match '+' as a character your re will be '\+'

Python - Raw String Literals

The only way to put in a single quote into a string started with a single quote is to escape it. Thus, both raw and regular string literals will allow escaping of quote characters when you have an unescaped backslash followed by a quote character. Because of the requirement that there must be a way to express single (or double) quotes inside string literals that begin with single (or double) quotes, the string literal '\' is not legal, whether you use a raw or regular string literal.

To get any arbitrary string with an odd number of literal backslashes, I believe the best way is to use regular string literals. This is because trying to use r'\\' will work, but it will give you a string with two backslashes instead of one:

>>> '\\' # A single literal backslash.
'\\'
>>> len('\\')
1
>>> r'\\' # Two literal backslashes, 2 is even so this is doable with raw.
'\\\\'
>>> len(r'\\')
2
>>> '\\'*3 # Three literal backslashes, only doable with ordinary literals.
'\\\\\\'
>>> len('\\'*3)
3

This answer is only meant to complement the other one.

Python: Trailing backslash in raw strings

From the documentation,

Specifically, a raw string 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 string, not as a line continuation.

Python raw strings and trailing backslash

It's a FAQ.

And in response to "you really want your string to end with a backslash. There's no way to do that in a 'raw' string.": the FAQ shows how to workaround it.

>>> r'ab\c' '\\' == 'ab\\c\\'
True
>>>

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