:mod:`ure` -- simple regular expressions ======================================== .. module:: ure :synopsis: regular expressions |see_cpython_module| :mod:`python:re`. This module implements regular expression operations. Regular expression syntax supported is a subset of CPython ``re`` module (and actually is a subset of POSIX extended regular expressions). Supported operators and special sequences are: ``.`` Match any character. ``[...]`` Match set of characters. Individual characters and ranges are supported, including negated sets (e.g. ``[^a-c]``). ``^`` Match the start of the string. ``$`` Match the end of the string. ``?`` Match zero or one of the previous sub-pattern. ``*`` Match zero or more of the previous sub-pattern. ``+`` Match one or more of the previous sub-pattern. ``??`` Non-greedy version of ``?``, match zero or one, with the preference for zero. ``*?`` Non-greedy version of ``*``, match zero or more, with the preference for the shortest match. ``+?`` Non-greedy version of ``+``, match one or more, with the preference for the shortest match. ``|`` Match either the left-hand side or the right-hand side sub-patterns of this operator. ``(...)`` Grouping. Each group is capturing (a substring it captures can be accessed with `match.group()` method). ``\d`` Matches digit. Equivalent to ``[0-9]``. ``\D`` Matches non-digit. Equivalent to ``[^0-9]``. ``\s`` Matches whitespace. Equivalent to ``[ \t-\r]``. ``\S`` Matches non-whitespace. Equivalent to ``[^ \t-\r]``. ``\w`` Matches "word characters" (ASCII only). Equivalent to ``[A-Za-z0-9_]``. ``\W`` Matches non "word characters" (ASCII only). Equivalent to ``[^A-Za-z0-9_]``. ``\`` Escape character. Any other character following the backslash, except for those listed above, is taken literally. For example, ``\*`` is equivalent to literal ``*`` (not treated as the ``*`` operator). Note that ``\r``, ``\n``, etc. are not handled specially, and will be equivalent to literal letters ``r``, ``n``, etc. Due to this, it's not recommended to use raw Python strings (``r""``) for regular expressions. For example, ``r"\r\n"`` when used as the regular expression is equivalent to ``"rn"``. To match CR character followed by LF, use ``"\r\n"``. **NOT SUPPORTED**: * counted repetitions (``{m,n}``) * named groups (``(?P...)``) * non-capturing groups (``(?:...)``) * more advanced assertions (``\b``, ``\B``) * special character escapes like ``\r``, ``\n`` - use Python's own escaping instead * etc. Example:: import ure # As ure doesn't support escapes itself, use of r"" strings is not # recommended. regex = ure.compile("[\r\n]") regex.split("line1\rline2\nline3\r\n") # Result: # ['line1', 'line2', 'line3', '', ''] Functions --------- .. function:: compile(regex_str, [flags]) Compile regular expression, return `regex ` object. .. function:: match(regex_str, string) Compile *regex_str* and match against *string*. Match always happens from starting position in a string. .. function:: search(regex_str, string) Compile *regex_str* and search it in a *string*. Unlike `match`, this will search string for first position which matches regex (which still may be 0 if regex is anchored). .. function:: sub(regex_str, replace, string, count=0, flags=0, /) Compile *regex_str* and search for it in *string*, replacing all matches with *replace*, and returning the new string. *replace* can be a string or a function. If it is a string then escape sequences of the form ``\`` and ``\g`` can be used to expand to the corresponding group (or an empty string for unmatched groups). If *replace* is a function then it must take a single argument (the match) and should return a replacement string. If *count* is specified and non-zero then substitution will stop after this many substitutions are made. The *flags* argument is ignored. Note: availability of this function depends on :term:`MicroPython port`. .. data:: DEBUG Flag value, display debug information about compiled expression. (Availability depends on :term:`MicroPython port`.) .. _regex: Regex objects ------------- Compiled regular expression. Instances of this class are created using `ure.compile()`. .. method:: regex.match(string) regex.search(string) regex.sub(replace, string, count=0, flags=0, /) Similar to the module-level functions :meth:`match`, :meth:`search` and :meth:`sub`. Using methods is (much) more efficient if the same regex is applied to multiple strings. .. method:: regex.split(string, max_split=-1, /) Split a *string* using regex. If *max_split* is given, it specifies maximum number of splits to perform. Returns list of strings (there may be up to *max_split+1* elements if it's specified). Match objects ------------- Match objects as returned by `match()` and `search()` methods, and passed to the replacement function in `sub()`. .. method:: match.group(index) Return matching (sub)string. *index* is 0 for entire match, 1 and above for each capturing group. Only numeric groups are supported. .. method:: match.groups() Return a tuple containing all the substrings of the groups of the match. Note: availability of this method depends on :term:`MicroPython port`. .. method:: match.start([index]) match.end([index]) Return the index in the original string of the start or end of the substring group that was matched. *index* defaults to the entire group, otherwise it will select a group. Note: availability of these methods depends on :term:`MicroPython port`. .. method:: match.span([index]) Returns the 2-tuple ``(match.start(index), match.end(index))``. Note: availability of this method depends on :term:`MicroPython port`.