[Python-3000-checkins] r65903 - python/branches/py3k/Doc/library/re.rst
mark.summerfield
python-3000-checkins at python.org
Wed Aug 20 09:34:41 CEST 2008
Author: mark.summerfield
Date: Wed Aug 20 09:34:41 2008
New Revision: 65903
Log:
Revised all texts concerning the ASCII flag: (1) put Unicode case first
(since that's the default), (2) made all descriptions consistent, (3)
dropped mention of re.LOCALE in most places since it is not recommended.
Modified:
python/branches/py3k/Doc/library/re.rst
Modified: python/branches/py3k/Doc/library/re.rst
==============================================================================
--- python/branches/py3k/Doc/library/re.rst (original)
+++ python/branches/py3k/Doc/library/re.rst Wed Aug 20 09:34:41 2008
@@ -323,67 +323,78 @@
Matches only at the start of the string.
``\b``
- Matches the empty string, but only at the beginning or end of a word. A word is
- defined as a sequence of alphanumeric or underscore characters, so the end of a
- word is indicated by whitespace or a non-alphanumeric, non-underscore character.
- Note that ``\b`` is defined as the boundary between ``\w`` and ``\ W``, so the
- precise set of characters deemed to be alphanumeric depends on the values of the
- ``ASCII`` and ``LOCALE`` flags. Inside a character range, ``\b`` represents
- the backspace character, for compatibility with Python's string literals.
+ Matches the empty string, but only at the beginning or end of a word.
+ A word is defined as a sequence of Unicode alphanumeric or underscore
+ characters, so the end of a word is indicated by whitespace or a
+ non-alphanumeric, non-underscore Unicode character. Note that
+ formally, ``\b`` is defined as the boundary between a ``\w`` and a
+ ``\W`` character (or vice versa). By default Unicode alphanumerics
+ are the ones used, but this can be changed by using the :const:`ASCII`
+ flag. Inside a character range, ``\b`` represents the backspace
+ character, for compatibility with Python's string literals.
``\B``
Matches the empty string, but only when it is *not* at the beginning or end of a
- word. This is just the opposite of ``\b``, so is also subject to the settings
- of ``ASCII`` and ``LOCALE`` .
+ word. This is just the opposite of ``\b``, so word characters are
+ Unicode alphanumerics or the underscore, although this can be changed
+ by using the :const:`ASCII` flag.
``\d``
For Unicode (str) patterns:
- When the :const:`ASCII` flag is specified, matches any decimal digit; this
- is equivalent to the set ``[0-9]``. Otherwise, it will match whatever
- is classified as a digit in the Unicode character properties database
- (but this does include the standard ASCII digits and is thus a superset
- of [0-9]).
+ Matches any Unicode digit (which includes ``[0-9]``, and also many
+ other digit characters). If the :const:`ASCII` flag is used only
+ ``[0-9]`` is matched (but the flag affects the entire regular
+ expression, so in such cases using an explicit ``[0-9]`` may be a
+ better choice).
For 8-bit (bytes) patterns:
- Matches any decimal digit; this is equivalent to the set ``[0-9]``.
+ Matches any decimal digit; this is equivalent to ``[0-9]``.
``\D``
- Matches any character which is not a decimal digit. This is the
- opposite of ``\d`` and is therefore similarly subject to the settings of
- ``ASCII`` and ``LOCALE``.
+ Matches any character which is not a Unicode decimal digit. This is
+ the opposite of ``\d``. If the :const:`ASCII` flag is used this
+ becomes the equivalent of ``[^0-9]`` (but the flag affects the entire
+ regular expression, so in such cases using an explicit ``[^0-9]`` may
+ be a better choice).
``\s``
For Unicode (str) patterns:
- When the :const:`ASCII` flag is specified, matches only ASCII whitespace
- characters; this is equivalent to the set ``[ \t\n\r\f\v]``. Otherwise,
- it will match this set whatever is classified as space in the Unicode
- character properties database (including for example the non-breaking
- spaces mandated by typography rules in many languages).
+ Matches Unicode whitespace characters (which includes
+ ``[ \t\n\r\f\v]``, and also many other characters, for example the
+ non-breaking spaces mandated by typography rules in many
+ languages). If the :const:`ASCII` flag is used, only
+ ``[ \t\n\r\f\v]`` is matched (but the flag affects the entire
+ regular expression, so in such cases using an explicit
+ ``[ \t\n\r\f\v]`` may be a better choice).
+
For 8-bit (bytes) patterns:
Matches characters considered whitespace in the ASCII character set;
- this is equivalent to the set ``[ \t\n\r\f\v]``.
+ this is equivalent to ``[ \t\n\r\f\v]``.
``\S``
- Matches any character which is not a whitespace character. This is the
- opposite of ``\s`` and is therefore similarly subject to the settings of
- ``ASCII`` and ``LOCALE``.
+ Matches any character which is not a Unicode whitespace character. This is
+ the opposite of ``\s``. If the :const:`ASCII` flag is used this
+ becomes the equivalent of ``[^ \t\n\r\f\v]`` (but the flag affects the entire
+ regular expression, so in such cases using an explicit ``[^ \t\n\r\f\v]`` may
+ be a better choice).
``\w``
For Unicode (str) patterns:
- When the :const:`ASCII` flag is specified, this is equivalent to the set
- ``[a-zA-Z0-9_]``. Otherwise, it will match whatever is classified as
- alphanumeric in the Unicode character properties database (it will
- include most characters that can be part of a word in whatever language,
- as well as numbers and the underscore sign).
+ Matches Unicode word characters; this includes most characters
+ that can be part of a word in any language, as well as numbers and
+ the underscore. If the :const:`ASCII` flag is used, only
+ ``[a-zA-Z0-9_]`` is matched (but the flag affects the entire
+ regular expression, so in such cases using an explicit
+ ``[a-zA-Z0-9_]`` may be a better choice).
For 8-bit (bytes) patterns:
Matches characters considered alphanumeric in the ASCII character set;
- this is equivalent to the set ``[a-zA-Z0-9_]``. With :const:`LOCALE`,
- it will additionally match whatever characters are defined as
- alphanumeric for the current locale.
+ this is equivalent to ``[a-zA-Z0-9_]``.
``\W``
- Matches any character which is not an alphanumeric character. This is the
- opposite of ``\w`` and is therefore similarly subject to the settings of
- ``ASCII`` and ``LOCALE``.
+ Matches any character which is not a Unicode word character. This is
+ the opposite of ``\w``. If the :const:`ASCII` flag is used this
+ becomes the equivalent of ``[^a-zA-Z0-9_]`` (but the flag affects the
+ entire regular expression, so in such cases using an explicit
+ ``[^a-zA-Z0-9_]`` may be a better choice).
``\Z``
Matches only at the end of the string.
@@ -471,17 +482,12 @@
matching instead of full Unicode matching. This is only meaningful for
Unicode patterns, and is ignored for byte patterns.
- Note that the :const:`re.U` flag still exists (as well as its synonym
- :const:`re.UNICODE` and its embedded counterpart ``(?u)``), but it has
- become useless in Python 3.0.
- In previous Python versions, it was used to specify that
- matching had to be Unicode dependent (the default was ASCII matching in
- all circumstances). Starting from Python 3.0, the default is Unicode
- matching for Unicode strings (which can be changed by specifying the
- ``'a'`` flag), and ASCII matching for 8-bit strings. Further, Unicode
- dependent matching for 8-bit strings isn't allowed anymore and results
- in a ValueError.
-
+ Note that for backward compatibility, the :const:`re.U` flag still
+ exists (as well as its synonym :const:`re.UNICODE` and its embedded
+ counterpart ``(?u)``), but these are redundant in Python 3.0 since
+ matches are Unicode by default for strings (and Unicode matching
+ isn't allowed for bytes).
+
.. data:: I
IGNORECASE
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