PySWIP README

:Version: 0.2.3

:Maintainer: Rodrigo Starr rodrigo.starr@gmail.com

:Author: Yuce Tekol yucetekol@gmail.com Rodrigo Starr rodrigo.starr@gmail.com

:Project Website: http://code.google.com/p/pyswip

Introduction

PySWIP is a Python - SWI-Prolog bridge enabling to query SWI-Prolog in your Python programs. It features an (incomplete) SWI-Prolog foreign language interface, a utility class that makes it easy querying with Prolog and also a Pythonic interface.

Since PySWIP uses SWI-Prolog as a shared library and ctypes to access it, it doesn't require compilation to be installed.

Note that this version of PySWIP is slightly incompatible with 0.1.x versions.

Requirements:

Python 2.3 and higher.
ctypes 1.0 and higher.
SWI-Prolog 5.6.x and higher (most probably other versions will also work).
libpl as a shared library.
Works on Linux and Win32, should work for all POSIX.

Example (Using Prolog):

>>> from pyswip import Prolog
>>> prolog = Prolog()
>>> prolog.assertz("father(michael,john)")
>>> prolog.assertz("father(michael,gina)")
>>> list(prolog.query("father(michael,X)"))
[{'X': 'john'}, {'X': 'gina'}]
>>> for soln in prolog.query("father(X,Y)"):
...     print soln["X"], "is the father of", soln["Y"]
...
michael is the father of john
michael is the father of gina

Since version 0.1.3 of PySWIP, it is possible to register a Python function as a Prolog predicate through SWI-Prolog's foreign language interface.

Example (Foreign Functions):

from pyswip import Prolog, registerForeign

def hello(t):
    print "Hello,", t
hello.arity = 1

registerForeign(hello)

prolog = Prolog()
prolog.assertz("father(michael,john)")
prolog.assertz("father(michael,gina)")    
list(prolog.query("father(michael,X), hello(X)"))

Outputs: Hello, john Hello, gina

Since version 0.2, PySWIP contains a 'Pythonic' interface which allows writing predicates in pure Python (Note that interface is experimental.)

Example (Pythonic interface):

from pyswip import Functor, Variable, Query

assertz = Functor("assertz", 2)
father = Functor("father", 2)

call(assertz(father("michael","john")))
call(assertz(father("michael","gina")))

X = Variable()
q = Query(father("michael",X))
while q.nextSolution():
    print "Hello,", X.value
q.closeQuery()

Outputs: Hello, john Hello, gina

The core functionality of Prolog.query is based on Nathan Denny's public domain prolog.py found at http://www.ahsc.arizona.edu/~schcats/projects/docs/prolog-0.2.0.html

Install

Please see INSTALL for detailed instructions.