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Merged
merged 6 commits into from
Dec 28, 2022
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gh-55688: Add note about ending backslashes for raw strings #94768

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0dc3888
Add note about ending backslashes for raw strings
slateny Jul 12, 2022
81d05a1
Be more specific with platform
slateny Oct 24, 2022
9e3d190
Move information on raw string and backslashes from tutorial to FAQ e…
slateny Dec 25, 2022
efad634
Use string concatenation over strip; add note on backslashed quotes i…
slateny Dec 25, 2022
b8e6594
Reword text and move to faq
slateny Dec 28, 2022
3b0de27
improve wording slightly
hauntsaninja Dec 28, 2022
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40 changes: 40 additions & 0 deletions Doc/faq/programming.rst
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Expand Up @@ -1019,6 +1019,46 @@ 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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5 changes: 5 additions & 0 deletions Doc/tutorial/introduction.rst
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Expand Up @@ -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
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