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author | Devtools Arcadia <arcadia-devtools@yandex-team.ru> | 2022-02-07 18:08:42 +0300 |
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committer | Devtools Arcadia <arcadia-devtools@mous.vla.yp-c.yandex.net> | 2022-02-07 18:08:42 +0300 |
commit | 1110808a9d39d4b808aef724c861a2e1a38d2a69 (patch) | |
tree | e26c9fed0de5d9873cce7e00bc214573dc2195b7 /contrib/python/pyparsing/py3/README.rst | |
download | ydb-1110808a9d39d4b808aef724c861a2e1a38d2a69.tar.gz |
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diff --git a/contrib/python/pyparsing/py3/README.rst b/contrib/python/pyparsing/py3/README.rst new file mode 100644 index 0000000000..f51c9ddd1b --- /dev/null +++ b/contrib/python/pyparsing/py3/README.rst @@ -0,0 +1,76 @@ +PyParsing -- A Python Parsing Module +==================================== + +|Build Status| |Coverage| + +Introduction +============ + +The pyparsing module is an alternative approach to creating and +executing simple grammars, vs. the traditional lex/yacc approach, or the +use of regular expressions. The pyparsing module provides a library of +classes that client code uses to construct the grammar directly in +Python code. + +*[Since first writing this description of pyparsing in late 2003, this +technique for developing parsers has become more widespread, under the +name Parsing Expression Grammars - PEGs. See more information on PEGs* +`here <https://en.wikipedia.org/wiki/Parsing_expression_grammar>`__ +*.]* + +Here is a program to parse ``"Hello, World!"`` (or any greeting of the form +``"salutation, addressee!"``): + +.. code:: python + + from pyparsing import Word, alphas + greet = Word(alphas) + "," + Word(alphas) + "!" + hello = "Hello, World!" + print(hello, "->", greet.parseString(hello)) + +The program outputs the following:: + + Hello, World! -> ['Hello', ',', 'World', '!'] + +The Python representation of the grammar is quite readable, owing to the +self-explanatory class names, and the use of '+', '|' and '^' operator +definitions. + +The parsed results returned from ``parseString()`` is a collection of type +``ParseResults``, which can be accessed as a +nested list, a dictionary, or an object with named attributes. + +The pyparsing module handles some of the problems that are typically +vexing when writing text parsers: + +- extra or missing whitespace (the above program will also handle ``"Hello,World!"``, ``"Hello , World !"``, etc.) +- quoted strings +- embedded comments + +The examples directory includes a simple SQL parser, simple CORBA IDL +parser, a config file parser, a chemical formula parser, and a four- +function algebraic notation parser, among many others. + +Documentation +============= + +There are many examples in the online docstrings of the classes +and methods in pyparsing. You can find them compiled into `online docs <https://pyparsing-docs.readthedocs.io/en/latest/>`__. Additional +documentation resources and project info are listed in the online +`GitHub wiki <https://github.com/pyparsing/pyparsing/wiki>`__. An +entire directory of examples can be found `here <https://github.com/pyparsing/pyparsing/tree/master/examples>`__. + +License +======= + +MIT License. See header of the `pyparsing.py <https://github.com/pyparsing/pyparsing/blob/master/pyparsing/__init__.py#L1-L23>`__ file. + +History +======= + +See `CHANGES <https://github.com/pyparsing/pyparsing/blob/master/CHANGES>`__ file. + +.. |Build Status| image:: https://github.com/pyparsing/pyparsing/actions/workflows/ci.yml/badge.svg + :target: https://github.com/pyparsing/pyparsing/actions/workflows/ci.yml +.. |Coverage| image:: https://codecov.io/gh/pyparsing/pyparsing/branch/master/graph/badge.svg + :target: https://codecov.io/gh/pyparsing/pyparsing |