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The pyparsing module is an alternative approach to creating and executingsimple grammars, vs. the traditional lex/yacc approach, or the use ofregular expressions. The pyparsing module provides a library of classesthat client code uses to construct the grammar directly in Python code.

Here is a program to parse "Hello, World!" (or any greeting of the form"salutation, addressee!"):

frompyparsingimportWord,alphasgreet=Word(alphas )+","+Word(alphas )+"!"hello="Hello, World!"printhello,"->",greet.parseString(hello )

The program outputs the following:

Hello, World! -> ['Hello', ',', 'World', '!']

The Python representation of the grammar is quite readable, owing to theself-explanatory class names, and the use of '+', '|' and '^' operatordefinitions.

The parsed results returned from parseString() can be accessed as anested list, a dictionary, or an object with named attributes.

The pyparsing module handles some of the problems that are typicallyvexing when writing text parsers:

• extra or missing whitespace (the above program will also handle"Hello,World!", "Hello , World !", etc.)
• quoted strings
• embedded comments

The .zip file includes examples of a simple SQL parser, simple CORBA IDLparser, a config file parser, a chemical formula parser, and a four-function algebraic notation parser. It also includes a simple how-todocument, and a UML class diagram of the library's classes.

Do the usual:

python setup.py install

(pyparsing requires Python 2.6 or later.)

Or corresponding commands using pip, easy_install, or wheel:

pip install pyparsingeasy_install pyparsingwheel install pyparsing

See:

HowToUsePyparsing.html

MIT License. See header of pyparsing.py

See CHANGES file.