A parser combinator library (and soon-to-be formatter combinator library as well) that's easy to use and that provides informative error messages.

## Project description

Parcon is a parser combinator library. It can be used for parsing both normal text and binary data. It’s designed to be easy to use and to provide informative error messages.

All of the classes, and most of the functions, in Parcon are comprehensively documented. The best place to look for help is in Parcon’s module documentation.

Here’s an example of a simple expression evaluator written using Parcon:

from parcon import * from decimal import Decimal import operator expr = Forward() number = (+Digit() + -(SignificantLiteral(“.”) + +Digit()))[flatten][“”.join][Decimal] term = number | “(” + expr + “)” term = InfixExpr(term, [(“*”, operator.mul), (“/”, operator.truediv)]) term = InfixExpr(term, [(“+”, operator.add), (“-“, operator.sub)]) expr << term

This expression evaluator can be used thus:

print expr.parseString(“1+2”) # prints 3 print expr.parseString(“1+2+3”) # prints 6 print expr.parseString(“1+2+3+4”) # prints 10 print expr.parseString(“3*4”) # prints 12 print expr.parseString(“5+3*4”) # prints 17 print expr.parseString(“(5+3)*4”) # prints 32 print expr.parseString(“10/4”) # prints 2.5