gh-55688: Add note about ending backslashes for raw strings (#94768)

Co-authored-by: hauntsaninja <hauntsaninja@gmail.com>
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Stanley 2022-12-27 21:30:42 -08:00 committed by GitHub
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@ -1026,6 +1026,46 @@ What does 'UnicodeDecodeError' or 'UnicodeEncodeError' error mean?
See the :ref:`unicode-howto`.
.. _faq-programming-raw-string-backslash:
Can I end a raw string with an odd number of backslashes?
---------------------------------------------------------
A raw string ending with an odd number of backslashes will escape the string's quote::
>>> r'C:\this\will\not\work\'
File "<stdin>", line 1
r'C:\this\will\not\work\'
^
SyntaxError: unterminated string literal (detected at line 1)
There are several workarounds for this. One is to use regular strings and double
the backslashes::
>>> 'C:\\this\\will\\work\\'
'C:\\this\\will\\work\\'
Another is to concatenate a regular string containing an escaped backslash to the
raw string::
>>> r'C:\this\will\work' '\\'
'C:\\this\\will\\work\\'
It is also possible to use :func:`os.path.join` to append a backslash on Windows::
>>> os.path.join(r'C:\this\will\work', '')
'C:\\this\\will\\work\\'
Note that while a backslash will "escape" a quote for the purposes of
determining where the raw string ends, no escaping occurs when interpreting the
value of the raw string. That is, the backslash remains present in the value of
the raw string::
>>> r'backslash\'preserved'
"backslash\\'preserved"
Also see the specification in the :ref:`language reference <strings>`.
Performance
===========

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@ -189,6 +189,11 @@ the first quote::
>>> print(r'C:\some\name') # note the r before the quote
C:\some\name
There is one subtle aspect to raw strings: a raw string may not end in
an odd number of ``\`` characters; see
:ref:`the FAQ entry <faq-programming-raw-string-backslash>` for more information
and workarounds.
String literals can span multiple lines. One way is using triple-quotes:
``"""..."""`` or ``'''...'''``. End of lines are automatically
included in the string, but it's possible to prevent this by adding a ``\`` at