bpo-32614: Modify re examples to use a raw string to prevent warning #5265

csabella · 2018-01-21T22:51:15Z

I only modified the examples that would have given a warning.

https://bugs.python.org/issue32614

ericvsmith

I agree with the ones that are invalid escape sequences. I can go either way on the '\n' examples, although I would personally not change them.

ericvsmith · 2018-01-21T22:58:38Z

Doc/howto/regex.rst

@@ -1233,7 +1233,7 @@ either side.  This takes the job beyond  :meth:`!replace`'s abilities.)

 Another common task is deleting every occurrence of a single character from a
 string or replacing it with another single character.  You might do this with
-something like ``re.sub('\n', ' ', S)``, but :meth:`~str.translate` is capable of
+something like ``re.sub(r'\n', ' ', S)``, but :meth:`~str.translate` is capable of


This change isn't strictly required, since '\n' is valid and won't raise a warning.

This is a bit tricky. '\n' produces a string of length 1. r'\n' produces a string of length 2. But re recognizes the same escapes that Python does, plus the additional ones, so the latter is also cooked down to a singles character, but later by re instead of Python itself. I think I would be inclined to omit 'r' but mention that it can be optionally added even when the literal only has standard escapes.

ericvsmith · 2018-01-21T22:58:48Z

Doc/library/re.rst

@@ -1398,7 +1398,7 @@ into a list with each nonempty line having its own entry:
 .. doctest::
   :options: +NORMALIZE_WHITESPACE

-   >>> entries = re.split("\n+", text)
+   >>> entries = re.split(r"\n+", text)


terryjreedy · 2018-01-26T21:58:08Z

I think you can add to this patch a generic comment about adding an 'r' prefix, as discussed on one of the lists (just today?). For instance, after the r'\d+' example.

"The 'r' prefix, making the literal a raw string literal, is needed because escape sequences in a normal 'cooked' string literal that are not recognized by Python, as opposed to re, now result in a deprecation warning and will eventually become a syntax error."

This should also be someplace in re.rst.

csabella · 2018-01-27T23:32:27Z

@terryjreedy I've made the changes, but there's a separate issue for adding the DeprecationWarning info to the docs - #5255

I had opened this one just to make sure the examples wouldn't produce a warning/error if someone was following them.

terryjreedy · 2018-02-02T04:20:18Z

If I understand, you think ready to go except for news entry. Please add.

The failure log just says "There was an error while trying to fetch the log." I clicked Restart button to see if there is a real problem that none of us see.

terryjreedy · 2018-02-02T05:01:58Z

The addition of

The `r` prefix, making the literal a raw string literal, is needed in this

causes

$ make check suspicious html SPHINXOPTS="-q -W -j4"
python3 tools/rstlint.py -i tools -i ./venv -i README.rst
[2] howto/regex.rst:472: default role used
1 problem with severity 2 found.
make: *** [check] Error 1

I don't know enough .rst to know the fix.

serhiy-storchaka · 2018-02-02T06:04:18Z

Doc/howto/regex.rst

   >>> p.findall('12 drummers drumming, 11 pipers piping, 10 lords a-leaping')
   ['12', '11', '10']

+The `r` prefix, making the literal a raw string literal, is needed in this


Use double backticks:

``r``

serhiy-storchaka · 2018-02-02T06:06:49Z

Doc/howto/regex.rst

@@ -327,6 +329,12 @@ backslashes are not handled in any special way in a string literal prefixed with
 while ``"\n"`` is a one-character string containing a newline. Regular
 expressions will often be written in Python code using this raw string notation.

+In addition, special escape sequences that are valid in ``re``, but not valid


Use RE or regular expressions instead of ``re``.

serhiy-storchaka · 2018-02-02T06:07:05Z

Doc/howto/regex.rst

   >>> p.findall('12 drummers drumming, 11 pipers piping, 10 lords a-leaping')
   ['12', '11', '10']

+The `r` prefix, making the literal a raw string literal, is needed in this
+example because escape sequences in a normal "cooked" string literal that are
+not recognized by Python, as opposed to ``re``, now result in a


Same as above.

csabella · 2018-02-02T12:51:29Z

@terryjreedy and @serhiy-storchaka Thank you! I've made the requested changes.

terryjreedy · 2018-02-02T20:45:24Z

Am I correct in thinking this should be backported to 3.7, but not 3.6? Serhiy, do you wish to merge this, or should I?

serhiy-storchaka · 2018-02-02T20:49:03Z

Please merge it Terry.

Warnings are emitted starting from 3.6. Examples in 3.6 should be fixed too.

miss-islington · 2018-02-02T21:16:29Z

Thanks @csabella for the PR, and @terryjreedy for merging it 🌮🎉.. I'm working now to backport this PR to: 3.6, 3.7.
🐍🍒⛏🤖

…ythonGH-5265) Modify RE examples in documentation to use raw strings to prevent DeprecationWarning. Add text to REGEX HOWTO to highlight the deprecation. Approved by Serhiy Storchaka. (cherry picked from commit 6677142) Co-authored-by: Cheryl Sabella <cheryl.sabella@gmail.com>

bedevere-bot · 2018-02-02T21:17:37Z

GH-5499 is a backport of this pull request to the 3.7 branch.

miss-islington · 2018-02-02T21:18:32Z

Sorry, @csabella and @terryjreedy, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 66771422d0541289d0b1287bc3c28e8b5609f6b4 3.6

…rning (pythonGH-5265) Modify RE examples in documentation to use raw strings to prevent DeprecationWarning. Add text to REGEX HOWTO to highlight the deprecation. Approved by Serhiy Storchaka. (cherry picked from commit 6677142)

…rning (pythonGH-5265) Modify RE examples in documentation to use raw strings to prevent DeprecationWarning. Add text to REGEX HOWTO to highlight the deprecation. Approved by Serhiy Storchaka.. (cherry picked from commit 6677142)

…H-5265) (#5499) Modify RE examples in documentation to use raw strings to prevent DeprecationWarning. Add text to REGEX HOWTO to highlight the deprecation. Approved by Serhiy Storchaka. (cherry picked from commit 6677142) Co-authored-by: Cheryl Sabella <cheryl.sabella@gmail.com>

…a… …rning (GH-5265) (GH-5500) Modify RE examples in documentation to use raw strings to prevent DeprecationWarning. Add text to REGEX HOWTO to highlight the deprecation. Approved by Serhiy Storchaka. (cherry picked from commit 6677142)

bpo-32614: Modify re examples to use a raw string to prevent warning

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the-knights-who-say-ni added the CLA signed label Jan 21, 2018

bedevere-bot added the awaiting review label Jan 21, 2018

ericvsmith reviewed Jan 21, 2018

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Remove raw strings from \n and clarify usage in HOWTO

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terryjreedy requested a review from serhiy-storchaka February 2, 2018 04:09

serhiy-storchaka reviewed Feb 2, 2018

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csabella added 2 commits February 2, 2018 07:43

Add blurb and correct markup

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Update 2018-02-02-07-41-57.bpo-32614.LSqzGw.rst

8c77a8b

terryjreedy approved these changes Feb 2, 2018

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bedevere-bot added awaiting merge and removed awaiting review labels Feb 2, 2018

serhiy-storchaka approved these changes Feb 2, 2018

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terryjreedy added the needs backport to 3.7 label Feb 2, 2018

serhiy-storchaka added the needs backport to 3.6 label Feb 2, 2018

terryjreedy merged commit 6677142 into python:master Feb 2, 2018

bedevere-bot removed the awaiting merge label Feb 2, 2018

bedevere-bot removed the needs backport to 3.7 label Feb 2, 2018

csabella deleted the redocs branch February 2, 2018 22:42

Mariatta mentioned this pull request Feb 13, 2018

bedevere did not remove needs backport label python/bedevere#95

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serhiy-storchaka removed the needs backport to 3.6 label Mar 31, 2018

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bpo-32614: Modify re examples to use a raw string to prevent warning #5265

bpo-32614: Modify re examples to use a raw string to prevent warning #5265

csabella commented Jan 21, 2018 •

edited by bedevere-bot

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miss-islington commented Feb 2, 2018

bpo-32614: Modify re examples to use a raw string to prevent warning #5265

bpo-32614: Modify re examples to use a raw string to prevent warning #5265

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csabella commented Feb 2, 2018

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csabella commented Jan 21, 2018 •

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