149 lines
4.2 KiB
ReStructuredText
149 lines
4.2 KiB
ReStructuredText
:mod:`ure` -- simple regular expressions
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========================================
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.. module:: ure
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:synopsis: regular expressions
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|see_cpython_module| :mod:`python:re`.
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This module implements regular expression operations. Regular expression
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syntax supported is a subset of CPython ``re`` module (and actually is
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a subset of POSIX extended regular expressions).
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Supported operators are:
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``'.'``
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Match any character.
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``'[...]'``
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Match set of characters. Individual characters and ranges are supported,
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including negated sets (e.g. ``[^a-c]``).
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``'^'``
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Match the start of the string.
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``'$'``
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Match the end of the string.
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``'?'``
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Match zero or one of the previous entity.
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``'*'``
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Match zero or more of the previous entity.
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``'+'``
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Match one or more of the previous entity.
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``'??'``
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``'*?'``
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``'+?'``
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``'|'``
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Match either the LHS or the RHS of this operator.
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``'(...)'``
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Grouping. Each group is capturing (a substring it captures can be accessed
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with `match.group()` method).
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**NOT SUPPORTED**: Counted repetitions (``{m,n}``), more advanced assertions
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(``\b``, ``\B``), named groups (``(?P<name>...)``), non-capturing groups
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(``(?:...)``), etc.
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Functions
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---------
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.. function:: compile(regex_str, [flags])
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Compile regular expression, return `regex <regex>` object.
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.. function:: match(regex_str, string)
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Compile *regex_str* and match against *string*. Match always happens
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from starting position in a string.
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.. function:: search(regex_str, string)
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Compile *regex_str* and search it in a *string*. Unlike `match`, this will search
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string for first position which matches regex (which still may be
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0 if regex is anchored).
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.. function:: sub(regex_str, replace, string, count=0, flags=0)
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Compile *regex_str* and search for it in *string*, replacing all matches
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with *replace*, and returning the new string.
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*replace* can be a string or a function. If it is a string then escape
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sequences of the form ``\<number>`` and ``\g<number>`` can be used to
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expand to the corresponding group (or an empty string for unmatched groups).
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If *replace* is a function then it must take a single argument (the match)
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and should return a replacement string.
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If *count* is specified and non-zero then substitution will stop after
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this many substitutions are made. The *flags* argument is ignored.
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Note: availability of this function depends on `MicroPython port`.
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.. data:: DEBUG
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Flag value, display debug information about compiled expression.
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(Availability depends on `MicroPython port`.)
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.. _regex:
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Regex objects
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-------------
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Compiled regular expression. Instances of this class are created using
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`ure.compile()`.
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.. method:: regex.match(string)
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regex.search(string)
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regex.sub(replace, string, count=0, flags=0)
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Similar to the module-level functions :meth:`match`, :meth:`search`
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and :meth:`sub`.
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Using methods is (much) more efficient if the same regex is applied to
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multiple strings.
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.. method:: regex.split(string, max_split=-1)
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Split a *string* using regex. If *max_split* is given, it specifies
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maximum number of splits to perform. Returns list of strings (there
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may be up to *max_split+1* elements if it's specified).
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Match objects
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-------------
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Match objects as returned by `match()` and `search()` methods, and passed
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to the replacement function in `sub()`.
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.. method:: match.group([index])
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Return matching (sub)string. *index* is 0 for entire match,
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1 and above for each capturing group. Only numeric groups are supported.
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.. method:: match.groups()
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Return a tuple containing all the substrings of the groups of the match.
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Note: availability of this method depends on `MicroPython port`.
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.. method:: match.start([index])
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match.end([index])
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Return the index in the original string of the start or end of the
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substring group that was matched. *index* defaults to the entire
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group, otherwise it will select a group.
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Note: availability of these methods depends on `MicroPython port`.
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.. method:: match.span([index])
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Returns the 2-tuple ``(match.start(index), match.end(index))``.
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Note: availability of this method depends on `MicroPython port`.
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