[Python-checkins] bpo-32614: Modify re examples to use a raw string to prevent warning (GH-5265)
Terry Jan Reedy
webhook-mailer at python.org
Fri Feb 2 16:16:36 EST 2018
https://github.com/python/cpython/commit/66771422d0541289d0b1287bc3c28e8b5609f6b4
commit: 66771422d0541289d0b1287bc3c28e8b5609f6b4
branch: master
author: Cheryl Sabella <cheryl.sabella at gmail.com>
committer: Terry Jan Reedy <tjreedy at udel.edu>
date: 2018-02-02T16:16:27-05:00
summary:
bpo-32614: Modify re examples to use a raw string to prevent warning (GH-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.
files:
A Misc/NEWS.d/next/Documentation/2018-02-02-07-41-57.bpo-32614.LSqzGw.rst
M Doc/howto/regex.rst
M Doc/howto/unicode.rst
M Doc/library/re.rst
diff --git a/Doc/howto/regex.rst b/Doc/howto/regex.rst
index 87a6b1aba59f..bdf687ee4551 100644
--- a/Doc/howto/regex.rst
+++ b/Doc/howto/regex.rst
@@ -289,6 +289,8 @@ Putting REs in strings keeps the Python language simpler, but has one
disadvantage which is the topic of the next section.
+.. _the-backslash-plague:
+
The Backslash Plague
--------------------
@@ -327,6 +329,13 @@ 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 regular expressions,
+but not valid as Python string literals, now result in a
+:exc:`DeprecationWarning` and will eventually become a :exc:`SyntaxError`,
+which means the sequences will be invalid if raw string notation or escaping
+the backslashes isn't used.
+
+
+-------------------+------------------+
| Regular String | Raw string |
+===================+==================+
@@ -457,10 +466,16 @@ In actual programs, the most common style is to store the
Two pattern methods return all of the matches for a pattern.
:meth:`~re.Pattern.findall` returns a list of matching strings::
- >>> p = re.compile('\d+')
+ >>> p = re.compile(r'\d+')
>>> 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 regular expressions, now result in a
+:exc:`DeprecationWarning` and will eventually become a :exc:`SyntaxError`. See
+:ref:`the-backslash-plague`.
+
:meth:`~re.Pattern.findall` has to create the entire list before it can be returned as the
result. The :meth:`~re.Pattern.finditer` method returns a sequence of
:ref:`match object <match-objects>` instances as an :term:`iterator`::
@@ -1096,11 +1111,11 @@ following calls::
The module-level function :func:`re.split` adds the RE to be used as the first
argument, but is otherwise the same. ::
- >>> re.split('[\W]+', 'Words, words, words.')
+ >>> re.split(r'[\W]+', 'Words, words, words.')
['Words', 'words', 'words', '']
- >>> re.split('([\W]+)', 'Words, words, words.')
+ >>> re.split(r'([\W]+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '']
- >>> re.split('[\W]+', 'Words, words, words.', 1)
+ >>> re.split(r'[\W]+', 'Words, words, words.', 1)
['Words', 'words, words.']
diff --git a/Doc/howto/unicode.rst b/Doc/howto/unicode.rst
index d4b8f8d2204a..093f4454af1d 100644
--- a/Doc/howto/unicode.rst
+++ b/Doc/howto/unicode.rst
@@ -463,7 +463,7 @@ The string in this example has the number 57 written in both Thai and
Arabic numerals::
import re
- p = re.compile('\d+')
+ p = re.compile(r'\d+')
s = "Over \u0e55\u0e57 57 flavours"
m = p.search(s)
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index 9b175f4e9675..83ebe7db01ad 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -345,7 +345,7 @@ The special characters are:
This example looks for a word following a hyphen:
- >>> m = re.search('(?<=-)\w+', 'spam-egg')
+ >>> m = re.search(r'(?<=-)\w+', 'spam-egg')
>>> m.group(0)
'egg'
diff --git a/Misc/NEWS.d/next/Documentation/2018-02-02-07-41-57.bpo-32614.LSqzGw.rst b/Misc/NEWS.d/next/Documentation/2018-02-02-07-41-57.bpo-32614.LSqzGw.rst
new file mode 100644
index 000000000000..9e9f3e3a74df
--- /dev/null
+++ b/Misc/NEWS.d/next/Documentation/2018-02-02-07-41-57.bpo-32614.LSqzGw.rst
@@ -0,0 +1,3 @@
+Modify RE examples in documentation to use raw strings to prevent
+:exc:`DeprecationWarning` and add text to REGEX HOWTO to highlight the
+deprecation.
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