bpo-38975: Add dedicated anchor for regexp syntax elements
This commit is contained in:
Baptiste Mispelon
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8b787964e0
commit
d711127135
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@ -96,6 +96,7 @@ the expression ``(?:a{6})*`` matches any multiple of six ``'a'`` characters.
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The special characters are:
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.. _syntax-dot:
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.. index:: single: . (dot); in regular expressions
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``.``
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@ -103,12 +104,14 @@ The special characters are:
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the :const:`DOTALL` flag has been specified, this matches any character
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including a newline.
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.. _syntax-caret:
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.. index:: single: ^ (caret); in regular expressions
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``^``
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(Caret.) Matches the start of the string, and in :const:`MULTILINE` mode also
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matches immediately after each newline.
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.. _syntax-dollar:
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.. index:: single: $ (dollar); in regular expressions
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``$``
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@ -120,6 +123,7 @@ The special characters are:
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a single ``$`` in ``'foo\n'`` will find two (empty) matches: one just before
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the newline, and one at the end of the string.
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.. _syntax-asterisk:
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.. index:: single: * (asterisk); in regular expressions
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``*``
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@ -127,6 +131,7 @@ The special characters are:
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many repetitions as are possible. ``ab*`` will match 'a', 'ab', or 'a' followed
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by any number of 'b's.
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.. _syntax-plus:
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.. index:: single: + (plus); in regular expressions
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``+``
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@ -134,12 +139,14 @@ The special characters are:
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``ab+`` will match 'a' followed by any non-zero number of 'b's; it will not
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match just 'a'.
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.. _syntax-question-mark:
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.. index:: single: ? (question mark); in regular expressions
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``?``
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Causes the resulting RE to match 0 or 1 repetitions of the preceding RE.
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``ab?`` will match either 'a' or 'ab'.
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.. _syntax-non-greedy:
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.. index::
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single: *?; in regular expressions
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single: +?; in regular expressions
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@ -154,6 +161,7 @@ The special characters are:
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characters as possible will be matched. Using the RE ``<.*?>`` will match
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only ``'<a>'``.
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.. _syntax-curly-brackets:
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.. index::
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single: {} (curly brackets); in regular expressions
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@ -178,6 +186,7 @@ The special characters are:
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6-character string ``'aaaaaa'``, ``a{3,5}`` will match 5 ``'a'`` characters,
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while ``a{3,5}?`` will only match 3 characters.
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.. _syntax-backslash:
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.. index:: single: \ (backslash); in regular expressions
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``\``
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@ -193,6 +202,7 @@ The special characters are:
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is complicated and hard to understand, so it's highly recommended that you use
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raw strings for all but the simplest expressions.
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.. _syntax-square-brackets:
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.. index::
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single: [] (square brackets); in regular expressions
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@ -253,6 +263,7 @@ The special characters are:
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:exc:`FutureWarning` is raised if a character set contains constructs
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that will change semantically in the future.
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.. _syntax-vertical-bar:
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.. index:: single: | (vertical bar); in regular expressions
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``|``
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@ -266,6 +277,7 @@ The special characters are:
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greedy. To match a literal ``'|'``, use ``\|``, or enclose it inside a
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character class, as in ``[|]``.
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.. _syntax-parentheses:
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.. index::
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single: () (parentheses); in regular expressions
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@ -276,6 +288,7 @@ The special characters are:
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special sequence, described below. To match the literals ``'('`` or ``')'``,
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use ``\(`` or ``\)``, or enclose them inside a character class: ``[(]``, ``[)]``.
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.. _syntax-extension:
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.. index:: single: (?; in regular expressions
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``(?...)``
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@ -285,6 +298,8 @@ The special characters are:
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group; ``(?P<name>...)`` is the only exception to this rule. Following are the
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currently supported extensions.
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.. _syntax-inline-flags:
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``(?aiLmsux)``
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(One or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``,
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``'s'``, ``'u'``, ``'x'``.) The group matches the empty string; the
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@ -299,6 +314,7 @@ The special characters are:
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:func:`re.compile` function. Flags should be used first in the
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expression string.
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.. _syntax-non-capturing:
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.. index:: single: (?:; in regular expressions
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``(?:...)``
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@ -307,6 +323,8 @@ The special characters are:
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*cannot* be retrieved after performing a match or referenced later in the
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pattern.
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.. _syntax-inline-flags-group:
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``(?aiLmsux-imsx:...)``
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(Zero or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``,
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``'s'``, ``'u'``, ``'x'``, optionally followed by ``'-'`` followed by
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@ -333,6 +351,7 @@ The special characters are:
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.. versionchanged:: 3.7
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The letters ``'a'``, ``'L'`` and ``'u'`` also can be used in a group.
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.. _syntax-named-capture:
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.. index:: single: (?P<; in regular expressions
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``(?P<name>...)``
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@ -360,17 +379,20 @@ The special characters are:
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| | * ``\1`` |
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+---------------------------------------+----------------------------------+
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.. _syntax-named-backreference:
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.. index:: single: (?P=; in regular expressions
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``(?P=name)``
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A backreference to a named group; it matches whatever text was matched by the
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earlier group named *name*.
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.. _syntax-comment:
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.. index:: single: (?#; in regular expressions
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``(?#...)``
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A comment; the contents of the parentheses are simply ignored.
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.. _syntax-lookahead:
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.. index:: single: (?=; in regular expressions
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``(?=...)``
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@ -378,6 +400,7 @@ The special characters are:
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called a :dfn:`lookahead assertion`. For example, ``Isaac (?=Asimov)`` will match
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``'Isaac '`` only if it's followed by ``'Asimov'``.
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.. _syntax-negative-lookahead:
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.. index:: single: (?!; in regular expressions
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``(?!...)``
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@ -385,6 +408,7 @@ The special characters are:
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For example, ``Isaac (?!Asimov)`` will match ``'Isaac '`` only if it's *not*
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followed by ``'Asimov'``.
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.. _syntax-lookbehind:
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.. index:: single: (?<=; in regular expressions
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``(?<=...)``
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@ -412,6 +436,7 @@ The special characters are:
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.. versionchanged:: 3.5
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Added support for group references of fixed length.
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.. _syntax-negative-lookbehind:
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.. index:: single: (?<!; in regular expressions
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``(?<!...)``
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@ -421,6 +446,8 @@ The special characters are:
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some fixed length. Patterns which start with negative lookbehind assertions may
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match at the beginning of the string being searched.
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.. _syntax-yes-no-pattern:
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``(?(id/name)yes-pattern|no-pattern)``
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Will try to match with ``yes-pattern`` if the group with given *id* or
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*name* exists, and with ``no-pattern`` if it doesn't. ``no-pattern`` is
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@ -435,6 +462,7 @@ If the ordinary character is not an ASCII digit or an ASCII letter, then the
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resulting RE will match the second character. For example, ``\$`` matches the
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character ``'$'``.
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.. _syntax-special-number:
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.. index:: single: \ (backslash); in regular expressions
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``\number``
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@ -447,11 +475,13 @@ character ``'$'``.
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``'['`` and ``']'`` of a character class, all numeric escapes are treated as
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characters.
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.. _syntax-special-uppercase-A:
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.. index:: single: \A; in regular expressions
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``\A``
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Matches only at the start of the string.
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.. _syntax-special-b:
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.. index:: single: \b; in regular expressions
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``\b``
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@ -468,6 +498,7 @@ character ``'$'``.
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Inside a character range, ``\b`` represents the backspace character, for
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compatibility with Python's string literals.
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.. _syntax-special-uppercase-B:
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.. index:: single: \B; in regular expressions
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``\B``
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@ -479,6 +510,7 @@ character ``'$'``.
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be changed by using the :const:`ASCII` flag. Word boundaries are
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determined by the current locale if the :const:`LOCALE` flag is used.
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.. _syntax-special-d:
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.. index:: single: \d; in regular expressions
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``\d``
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@ -491,6 +523,7 @@ character ``'$'``.
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For 8-bit (bytes) patterns:
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Matches any decimal digit; this is equivalent to ``[0-9]``.
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.. _syntax-special-uppercase-D:
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.. index:: single: \D; in regular expressions
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``\D``
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@ -498,6 +531,7 @@ character ``'$'``.
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the opposite of ``\d``. If the :const:`ASCII` flag is used this
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becomes the equivalent of ``[^0-9]``.
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.. _syntax-special-s:
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.. index:: single: \s; in regular expressions
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``\s``
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@ -512,6 +546,7 @@ character ``'$'``.
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Matches characters considered whitespace in the ASCII character set;
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this is equivalent to ``[ \t\n\r\f\v]``.
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.. _syntax-special-uppercase-S:
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.. index:: single: \S; in regular expressions
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``\S``
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@ -519,6 +554,7 @@ character ``'$'``.
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the opposite of ``\s``. If the :const:`ASCII` flag is used this
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becomes the equivalent of ``[^ \t\n\r\f\v]``.
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.. _syntax-special-w:
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.. index:: single: \w; in regular expressions
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``\w``
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@ -534,6 +570,7 @@ character ``'$'``.
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used, matches characters considered alphanumeric in the current locale
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and the underscore.
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.. _syntax-special-uppercase-W:
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.. index:: single: \W; in regular expressions
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``\W``
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@ -543,11 +580,13 @@ character ``'$'``.
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used, matches characters which are neither alphanumeric in the current locale
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nor the underscore.
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.. _syntax-special-uppercase-Z:
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.. index:: single: \Z; in regular expressions
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``\Z``
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Matches only at the end of the string.
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.. _syntax-special-py:
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.. index::
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single: \a; in regular expressions
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single: \b; in regular expressions
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