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 at
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() 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
at https://pyparsing-docs.readthedocs.io/en/latest/. Additional
documentation resources and project info are listed in the online
GitHub wiki, at https://github.com/pyparsing/pyparsing/wiki. An
entire directory of examples is at
https://github.com/pyparsing/pyparsing/tree/master/examples.
License
MIT License. See header of pyparsing.py
History
See CHANGES file.
.., Build Status, image:: https://travis-ci.org/pyparsing/pyparsing.svg?branch=master
:target: https://travis-ci.org/pyparsing/pyparsing
.., Coverage, image:: https://codecov.io/gh/pyparsing/pyparsing/branch/master/graph/badge.svg
:target: https://codecov.io/gh/pyparsing/pyparsing
