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Revised all texts concerning the ASCII flag: (1) put Unicode case first

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(since that's the default), (2) made all descriptions consistent, (3)
dropped mention of re.LOCALE in most places since it is not recommended.
This commit is contained in:
Mark Summerfield 2008-08-20 07:34:41 +00:00
parent 5ef6d18bdf
commit 6c4f617922
1 changed files with 55 additions and 49 deletions
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104
Doc/library/re.rst
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@ -323,67 +323,78 @@ the second character. For example, ``\$`` matches the character ``'$'``.
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 @@ form.
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