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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 is a program to parse
"Hello, World!" (or any greeting of the form
.. 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:
"Hello , World !", etc.)
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.
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
MIT License. See header of the
pyparsing.py <https://github.com/pyparsing/pyparsing/blob/master/pyparsing/__init__.py#L1-L23>__ file.
CHANGES <https://github.com/pyparsing/pyparsing/blob/master/CHANGES>__ file.
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