ptk 1.0.0

LR(1) parsing framework for Python

PTK - (c) Jérôme Laheurte 2015

Table of contents

• What is PTK ?

• Supported platforms

• Installation

• Sample usage

• Code samples

What is PTK ?

PTK is a LR(1) parser “generator” for Python. It is not actually a “generator” in the sense that it doesn’t output source code, using Python’s dynamic nature to build everything it needs at runtime instead.

This code is licensed under the GNU LGPL version 3.

Supported platforms

All unit tests pass on the following platforms/Python version:

	Linux	OSX	Windows
2.7	X	X	X
3.2	X		X
3.3			X
3.4			X
3.5		X

See the Buildbot for details.

Although Python 2.6 is not officially supported, it does work with a few minor code modifications, namely replacing functools.total_ordering with the backport to 2.6.

Installation

Using pip:

$ pip install -U ptk

From source:

$ wget https://pypi.python.org/packages/source/p/ptk/ptk-1.0.0.tar.gz
$ tar xjf ptk-1.0.0.tar.bz2; cd ptk-1.0.0
$ sudo python ./setup.py install

Sample usage

Four-operations integer calculator:

from ptk.parser import LRParser, production, leftAssoc
from ptk.lexer import ReLexer, token
import operator, six

@leftAssoc('+', '-')
@rightAssoc('*', '/')
class Parser(LRParser, ReLexer):
    @token('[1-9][0-9]*')
    def number(self, tok):
        tok.value = int(tok.value)
    @production('E -> number<n>')
    def litteral(self, n):
        return n
    @production('E -> "-" E<val>', priority='*')
    def minus(self, val):
        return -val
    @production('E -> "(" E<val> ")"')
    def paren(self, val):
        return val
    @production('E -> E<left> "+"<op> E<right>')
    @production('E -> E<left> "-"<op> E<right>')
    @production('E -> E<left> "*"<op> E<right>')
    @production('E -> E<left> "/"<op> E<right>')
    def binaryop(self, left, op, right):
        return {
            '+': operator.add,
            '-': operator.sub,
            '*': operator.mul,
            '/': operator.floordiv
            }[op](left, right)

parser = Parser()
while True:
    expr = six.moves.input('> ')
    print parser.parse(expr)

Code samples

The samples subdirectory in the source tree contains the aforementioned calculator and a script that generates a skeleton Python file from a Yacc or Bison grammar file.