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#10713: Improve documentation for \b and \B and add a few tests. Initial patch and tests by Martin Pool.

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Ezio Melotti 2012-02-29 11:48:44 +02:00
parent 62417a0354
commit 5a045b9f54
2 changed files with 40 additions and 8 deletions
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22
Doc/library/re.rst
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@ -330,16 +330,22 @@ the second character. For example, ``\$`` matches the character ``'$'``.
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.
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), or between ``\w`` and the beginning/end of the string.
This means that ``r'\bfoo\b'`` matches ``'foo'``, ``'foo.'``, ``'(foo)'``,
``'bar foo baz'`` but not ``'foobar'`` or ``'foo3'``.
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 word characters are
Matches the empty string, but only when it is *not* at the beginning or end
of a word. This means that ``r'py\B'`` matches ``'python'``, ``'py3'``,
``'py2'``, but not ``'py'``, ``'py.'``, or ``'py!'``.
``\B`` 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.