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bpo-38975: Add dedicated anchor for regexp syntax elements

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Baptiste Mispelon 2019-12-04 21:48:44 +01:00
parent 8b787964e0
commit d711127135
1 changed files with 39 additions and 0 deletions
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Doc/library/re.rst
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@ -96,6 +96,7 @@ the expression ``(?:a{6})*`` matches any multiple of six ``'a'`` characters.
The special characters are: The special characters are:
.. _syntax-dot:
.. index:: single: . (dot); in regular expressions .. index:: single: . (dot); in regular expressions
``.`` ``.``
@ -103,12 +104,14 @@ The special characters are:
the :const:`DOTALL` flag has been specified, this matches any character the :const:`DOTALL` flag has been specified, this matches any character
including a newline. including a newline.
.. _syntax-caret:
.. index:: single: ^ (caret); in regular expressions .. index:: single: ^ (caret); in regular expressions
``^`` ``^``
(Caret.) Matches the start of the string, and in :const:`MULTILINE` mode also (Caret.) Matches the start of the string, and in :const:`MULTILINE` mode also
matches immediately after each newline. matches immediately after each newline.
.. _syntax-dollar:
.. index:: single: $ (dollar); in regular expressions .. index:: single: $ (dollar); in regular expressions
``$`` ``$``
@ -120,6 +123,7 @@ The special characters are:
a single ``$`` in ``'foo\n'`` will find two (empty) matches: one just before a single ``$`` in ``'foo\n'`` will find two (empty) matches: one just before
the newline, and one at the end of the string. the newline, and one at the end of the string.
.. _syntax-asterisk:
.. index:: single: * (asterisk); in regular expressions .. index:: single: * (asterisk); in regular expressions
``*`` ``*``
@ -127,6 +131,7 @@ The special characters are:
many repetitions as are possible. ``ab*`` will match 'a', 'ab', or 'a' followed many repetitions as are possible. ``ab*`` will match 'a', 'ab', or 'a' followed
by any number of 'b's. by any number of 'b's.
.. _syntax-plus:
.. index:: single: + (plus); in regular expressions .. index:: single: + (plus); in regular expressions
``+`` ``+``
@ -134,12 +139,14 @@ The special characters are:
``ab+`` will match 'a' followed by any non-zero number of 'b's; it will not ``ab+`` will match 'a' followed by any non-zero number of 'b's; it will not
match just 'a'. match just 'a'.
.. _syntax-question-mark:
.. index:: single: ? (question mark); in regular expressions .. index:: single: ? (question mark); in regular expressions
``?`` ``?``
Causes the resulting RE to match 0 or 1 repetitions of the preceding RE. Causes the resulting RE to match 0 or 1 repetitions of the preceding RE.
``ab?`` will match either 'a' or 'ab'. ``ab?`` will match either 'a' or 'ab'.
.. _syntax-non-greedy:
.. index:: .. index::
single: *?; in regular expressions single: *?; in regular expressions
single: +?; in regular expressions single: +?; in regular expressions
@ -154,6 +161,7 @@ The special characters are:
characters as possible will be matched. Using the RE ``<.*?>`` will match characters as possible will be matched. Using the RE ``<.*?>`` will match
only ``'<a>'``. only ``'<a>'``.
.. _syntax-curly-brackets:
.. index:: .. index::
single: {} (curly brackets); in regular expressions single: {} (curly brackets); in regular expressions
@ -178,6 +186,7 @@ The special characters are:
6-character string ``'aaaaaa'``, ``a{3,5}`` will match 5 ``'a'`` characters, 6-character string ``'aaaaaa'``, ``a{3,5}`` will match 5 ``'a'`` characters,
while ``a{3,5}?`` will only match 3 characters. while ``a{3,5}?`` will only match 3 characters.
.. _syntax-backslash:
.. index:: single: \ (backslash); in regular expressions .. index:: single: \ (backslash); in regular expressions
``\`` ``\``
@ -193,6 +202,7 @@ The special characters are:
is complicated and hard to understand, so it's highly recommended that you use is complicated and hard to understand, so it's highly recommended that you use
raw strings for all but the simplest expressions. raw strings for all but the simplest expressions.
.. _syntax-square-brackets:
.. index:: .. index::
single: [] (square brackets); in regular expressions single: [] (square brackets); in regular expressions
@ -253,6 +263,7 @@ The special characters are:
:exc:`FutureWarning` is raised if a character set contains constructs :exc:`FutureWarning` is raised if a character set contains constructs
that will change semantically in the future. that will change semantically in the future.
.. _syntax-vertical-bar:
.. index:: single: | (vertical bar); in regular expressions .. index:: single: | (vertical bar); in regular expressions
``|`` ``|``
@ -266,6 +277,7 @@ The special characters are:
greedy. To match a literal ``'|'``, use ``\|``, or enclose it inside a greedy. To match a literal ``'|'``, use ``\|``, or enclose it inside a
character class, as in ``[|]``. character class, as in ``[|]``.
.. _syntax-parentheses:
.. index:: .. index::
single: () (parentheses); in regular expressions single: () (parentheses); in regular expressions
@ -276,6 +288,7 @@ The special characters are:
special sequence, described below. To match the literals ``'('`` or ``')'``, special sequence, described below. To match the literals ``'('`` or ``')'``,
use ``\(`` or ``\)``, or enclose them inside a character class: ``[(]``, ``[)]``. use ``\(`` or ``\)``, or enclose them inside a character class: ``[(]``, ``[)]``.
.. _syntax-extension:
.. index:: single: (?; in regular expressions .. index:: single: (?; in regular expressions
``(?...)`` ``(?...)``
@ -285,6 +298,8 @@ The special characters are:
group; ``(?P<name>...)`` is the only exception to this rule. Following are the group; ``(?P<name>...)`` is the only exception to this rule. Following are the
currently supported extensions. currently supported extensions.
.. _syntax-inline-flags:
``(?aiLmsux)`` ``(?aiLmsux)``
(One or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``, (One or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``,
``'s'``, ``'u'``, ``'x'``.) The group matches the empty string; the ``'s'``, ``'u'``, ``'x'``.) The group matches the empty string; the
@ -299,6 +314,7 @@ The special characters are:
:func:`re.compile` function. Flags should be used first in the :func:`re.compile` function. Flags should be used first in the
expression string. expression string.
.. _syntax-non-capturing:
.. index:: single: (?:; in regular expressions .. index:: single: (?:; in regular expressions
``(?:...)`` ``(?:...)``
@ -307,6 +323,8 @@ The special characters are:
*cannot* be retrieved after performing a match or referenced later in the *cannot* be retrieved after performing a match or referenced later in the
pattern. pattern.
.. _syntax-inline-flags-group:
``(?aiLmsux-imsx:...)`` ``(?aiLmsux-imsx:...)``
(Zero or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``, (Zero or more letters from the set ``'a'``, ``'i'``, ``'L'``, ``'m'``,
``'s'``, ``'u'``, ``'x'``, optionally followed by ``'-'`` followed by ``'s'``, ``'u'``, ``'x'``, optionally followed by ``'-'`` followed by
@ -333,6 +351,7 @@ The special characters are:
.. versionchanged:: 3.7 .. versionchanged:: 3.7
The letters ``'a'``, ``'L'`` and ``'u'`` also can be used in a group. The letters ``'a'``, ``'L'`` and ``'u'`` also can be used in a group.
.. _syntax-named-capture:
.. index:: single: (?P<; in regular expressions .. index:: single: (?P<; in regular expressions
``(?P<name>...)`` ``(?P<name>...)``
@ -360,17 +379,20 @@ The special characters are:
| | * ``\1`` | | | * ``\1`` |
+---------------------------------------+----------------------------------+ +---------------------------------------+----------------------------------+
.. _syntax-named-backreference:
.. index:: single: (?P=; in regular expressions .. index:: single: (?P=; in regular expressions
``(?P=name)`` ``(?P=name)``
A backreference to a named group; it matches whatever text was matched by the A backreference to a named group; it matches whatever text was matched by the
earlier group named *name*. earlier group named *name*.
.. _syntax-comment:
.. index:: single: (?#; in regular expressions .. index:: single: (?#; in regular expressions
``(?#...)`` ``(?#...)``
A comment; the contents of the parentheses are simply ignored. A comment; the contents of the parentheses are simply ignored.
.. _syntax-lookahead:
.. index:: single: (?=; in regular expressions .. index:: single: (?=; in regular expressions
``(?=...)`` ``(?=...)``
@ -378,6 +400,7 @@ The special characters are:
called a :dfn:`lookahead assertion`. For example, ``Isaac (?=Asimov)`` will match called a :dfn:`lookahead assertion`. For example, ``Isaac (?=Asimov)`` will match
``'Isaac '`` only if it's followed by ``'Asimov'``. ``'Isaac '`` only if it's followed by ``'Asimov'``.
.. _syntax-negative-lookahead:
.. index:: single: (?!; in regular expressions .. index:: single: (?!; in regular expressions
``(?!...)`` ``(?!...)``
@ -385,6 +408,7 @@ The special characters are:
For example, ``Isaac (?!Asimov)`` will match ``'Isaac '`` only if it's *not* For example, ``Isaac (?!Asimov)`` will match ``'Isaac '`` only if it's *not*
followed by ``'Asimov'``. followed by ``'Asimov'``.
.. _syntax-lookbehind:
.. index:: single: (?<=; in regular expressions .. index:: single: (?<=; in regular expressions
``(?<=...)`` ``(?<=...)``
@ -412,6 +436,7 @@ The special characters are:
.. versionchanged:: 3.5 .. versionchanged:: 3.5
Added support for group references of fixed length. Added support for group references of fixed length.
.. _syntax-negative-lookbehind:
.. index:: single: (?<!; in regular expressions .. index:: single: (?<!; in regular expressions
``(?<!...)`` ``(?<!...)``
@ -421,6 +446,8 @@ The special characters are:
some fixed length. Patterns which start with negative lookbehind assertions may some fixed length. Patterns which start with negative lookbehind assertions may
match at the beginning of the string being searched. match at the beginning of the string being searched.
.. _syntax-yes-no-pattern:
``(?(id/name)yes-pattern|no-pattern)`` ``(?(id/name)yes-pattern|no-pattern)``
Will try to match with ``yes-pattern`` if the group with given *id* or Will try to match with ``yes-pattern`` if the group with given *id* or
*name* exists, and with ``no-pattern`` if it doesn't. ``no-pattern`` is *name* exists, and with ``no-pattern`` if it doesn't. ``no-pattern`` is
@ -435,6 +462,7 @@ If the ordinary character is not an ASCII digit or an ASCII letter, then the
resulting RE will match the second character. For example, ``\$`` matches the resulting RE will match the second character. For example, ``\$`` matches the
character ``'$'``. character ``'$'``.
.. _syntax-special-number:
.. index:: single: \ (backslash); in regular expressions .. index:: single: \ (backslash); in regular expressions
``\number`` ``\number``
@ -447,11 +475,13 @@ character ``'$'``.
``'['`` and ``']'`` of a character class, all numeric escapes are treated as ``'['`` and ``']'`` of a character class, all numeric escapes are treated as
characters. characters.
.. _syntax-special-uppercase-A:
.. index:: single: \A; in regular expressions .. index:: single: \A; in regular expressions
``\A`` ``\A``
Matches only at the start of the string. Matches only at the start of the string.
.. _syntax-special-b:
.. index:: single: \b; in regular expressions .. index:: single: \b; in regular expressions
``\b`` ``\b``
@ -468,6 +498,7 @@ character ``'$'``.
Inside a character range, ``\b`` represents the backspace character, for Inside a character range, ``\b`` represents the backspace character, for
compatibility with Python's string literals. compatibility with Python's string literals.
.. _syntax-special-uppercase-B:
.. index:: single: \B; in regular expressions .. index:: single: \B; in regular expressions
``\B`` ``\B``
@ -479,6 +510,7 @@ character ``'$'``.
be changed by using the :const:`ASCII` flag. Word boundaries are be changed by using the :const:`ASCII` flag. Word boundaries are
determined by the current locale if the :const:`LOCALE` flag is used. determined by the current locale if the :const:`LOCALE` flag is used.
.. _syntax-special-d:
.. index:: single: \d; in regular expressions .. index:: single: \d; in regular expressions
``\d`` ``\d``
@ -491,6 +523,7 @@ character ``'$'``.
For 8-bit (bytes) patterns: For 8-bit (bytes) patterns:
Matches any decimal digit; this is equivalent to ``[0-9]``. Matches any decimal digit; this is equivalent to ``[0-9]``.
.. _syntax-special-uppercase-D:
.. index:: single: \D; in regular expressions .. index:: single: \D; in regular expressions
``\D`` ``\D``
@ -498,6 +531,7 @@ character ``'$'``.
the opposite of ``\d``. If the :const:`ASCII` flag is used this the opposite of ``\d``. If the :const:`ASCII` flag is used this
becomes the equivalent of ``[^0-9]``. becomes the equivalent of ``[^0-9]``.
.. _syntax-special-s:
.. index:: single: \s; in regular expressions .. index:: single: \s; in regular expressions
``\s`` ``\s``
@ -512,6 +546,7 @@ character ``'$'``.
Matches characters considered whitespace in the ASCII character set; Matches characters considered whitespace in the ASCII character set;
this is equivalent to ``[ \t\n\r\f\v]``. this is equivalent to ``[ \t\n\r\f\v]``.
.. _syntax-special-uppercase-S:
.. index:: single: \S; in regular expressions .. index:: single: \S; in regular expressions
``\S`` ``\S``
@ -519,6 +554,7 @@ character ``'$'``.
the opposite of ``\s``. If the :const:`ASCII` flag is used this the opposite of ``\s``. If the :const:`ASCII` flag is used this
becomes the equivalent of ``[^ \t\n\r\f\v]``. becomes the equivalent of ``[^ \t\n\r\f\v]``.
.. _syntax-special-w:
.. index:: single: \w; in regular expressions .. index:: single: \w; in regular expressions
``\w`` ``\w``
@ -534,6 +570,7 @@ character ``'$'``.
used, matches characters considered alphanumeric in the current locale used, matches characters considered alphanumeric in the current locale
and the underscore. and the underscore.
.. _syntax-special-uppercase-W:
.. index:: single: \W; in regular expressions .. index:: single: \W; in regular expressions
``\W`` ``\W``
@ -543,11 +580,13 @@ character ``'$'``.
used, matches characters which are neither alphanumeric in the current locale used, matches characters which are neither alphanumeric in the current locale
nor the underscore. nor the underscore.
.. _syntax-special-uppercase-Z:
.. index:: single: \Z; in regular expressions .. index:: single: \Z; in regular expressions
``\Z`` ``\Z``
Matches only at the end of the string. Matches only at the end of the string.
.. _syntax-special-py:
.. index:: .. index::
single: \a; in regular expressions single: \a; in regular expressions
single: \b; in regular expressions single: \b; in regular expressions