pyswip 0.2.1

PySWIP enables querying SWI-Prolog in your Python programs.

PySWIP 0.2.1
============

PySWIP is a GPL'd 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.

News
----

* Importing ``pyswip`` automatically initializes SWI-Prolog.
* Fixed a bug with querying lists with the new interface.

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.

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

Outputs:
Hello, john
Hello, gina