Skip to main content

pyparsing module - Classes and methods to define and execute parsing grammars

Project description

PyParsing – A Python Parsing Module

Version Build Status Coverage License Python versions pyparsing

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 .]

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() 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. Additional documentation resources and project info are listed in the online GitHub wiki. An entire directory of examples can be found here.

License

MIT License. See header of the pyparsing __init__.py file.

History

See CHANGES file.

Release history Release notifications | RSS feed

This version

3.1.2

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

pyparsing-3.1.2.tar.gz (889.6 kB view hashes)

Uploaded source

Built Distribution

pyparsing-3.1.2-py3-none-any.whl (103.2 kB view hashes)

Uploaded py3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page