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PyParsing -- A Python Parsing Module
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Introduction
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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.
Here is a program to parse "Hello, World!" (or any greeting of the form
"<salutation>, <addressee>!"):
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() 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 .zip file includes examples of a simple SQL parser, simple CORBA IDL
parser, a config file parser, a chemical formula parser, and a four-
function algebraic notation parser. It also includes a simple how-to
document, and a UML class diagram of the library's classes.
Installation
============
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 pyparsing
easy_install pyparsing
wheel install pyparsing
Documentation
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See:
HowToUsePyparsing.html
License
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MIT License. See header of pyparsing.py
History
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See CHANGES file.
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