The parsing module is an alternative approach to creating and executing
simple grammars, vs. the traditional lex/yacc approach, or the use of
regular expressions. The parsing 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
from parsing 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
The parsed results returned from parseString() can be accessed as a nested
list, a dictionary, or an object with named attributes.
The parsing 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.
The parsing module can be found at
Please let me know if you find this package helpful.
-- Paul McGuire