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| -rw-r--r-- | Doc/library/re.rst | 54 |
1 files changed, 30 insertions, 24 deletions
diff --git a/Doc/library/re.rst b/Doc/library/re.rst index 2c150cc..331ffa7 100644 --- a/Doc/library/re.rst +++ b/Doc/library/re.rst @@ -161,30 +161,36 @@ The special characters are: raw strings for all but the simplest expressions. ``[]`` - Used to indicate a set of characters. Characters can be listed individually, or - a range of characters can be indicated by giving two characters and separating - them by a ``'-'``. Special characters are not active inside sets. For example, - ``[akm$]`` will match any of the characters ``'a'``, ``'k'``, - ``'m'``, or ``'$'``; ``[a-z]`` will match any lowercase letter, and - ``[a-zA-Z0-9]`` matches any letter or digit. Character classes such - as ``\w`` or ``\S`` (defined below) are also acceptable inside a - range, although the characters they match depends on whether - :const:`ASCII` or :const:`LOCALE` mode is in force. If you want to - include a ``']'`` or a ``'-'`` inside a set, precede it with a - backslash, or place it as the first character. The pattern ``[]]`` - will match ``']'``, for example. - - You can match the characters not within a range by :dfn:`complementing` the set. - This is indicated by including a ``'^'`` as the first character of the set; - ``'^'`` elsewhere will simply match the ``'^'`` character. For example, - ``[^5]`` will match any character except ``'5'``, and ``[^^]`` will match any - character except ``'^'``. - - Note that inside ``[]`` the special forms and special characters lose - their meanings and only the syntaxes described here are valid. For - example, ``+``, ``*``, ``(``, ``)``, and so on are treated as - literals inside ``[]``, and backreferences cannot be used inside - ``[]``. + Used to indicate a set of characters. In a set: + + * Characters can be listed individually, e.g. ``[amk]`` will match ``'a'``, + ``'m'``, or ``'k'``. + + * Ranges of characters can be indicated by giving two characters and separating + them by a ``'-'``, for example ``[a-z]`` will match any lowercase ASCII letter, + ``[0-5][0-9]`` will match all the two-digits numbers from ``00`` to ``59``, and + ``[0-9A-Fa-f]`` will match any hexadecimal digit. If ``-`` is escaped (e.g. + ``[a\-z]``) or if it's placed as the first or last character (e.g. ``[a-]``), + it will match a literal ``'-'``. + + * Special characters lose their special meaning inside sets. For example, + ``[(+*)]`` will match any of the literal characters ``'('``, ``'+'``, + ``'*'``, or ``')'``. + + * Character classes such as ``\w`` or ``\S`` (defined below) are also accepted + inside a set, although the characters they match depends on whether + :const:`ASCII` or :const:`LOCALE` mode is in force. + + * Characters that are not within a range can be matched by :dfn:`complementing` + the set. If the first character of the set is ``'^'``, all the characters + that are *not* in the set will be matched. For example, ``[^5]`` will match + any character except ``'5'``, and ``[^^]`` will match any character except + ``'^'``. ``^`` has no special meaning if it's not the first character in + the set. + + * To match a literal ``']'`` inside a set, precede it with a backslash, or + place it at the beginning of the set. For example, both ``[()[\]{}]`` and + ``[]()[{}]`` will both match a parenthesis. ``'|'`` ``A|B``, where A and B can be arbitrary REs, creates a regular expression that |