Value Exchange Between Python and Prolog

String Interpolation from Python to Prolog

Currently there’s limited support for converting Python values automatically to Prolog via a string interpolation mechanism. This mechanism is available to be used with the following Prolog class methods:

• assertz

• asserta

• retract

• query

These methods take one string format argument, and zero or more arguments to replace placeholders with in the format to produce the final string. Placeholder is %p for all types.

The following types are recognized:

• String

• Integer

• Float

• Boolean

• pyswip.Atom

• pyswip.Variable

• Lists of the types above

Other types are converted to strings using the str function.

String Interpolation to Prolog

Python Value	String
str "Some value"	"Some value"
int 38	38
float 38.42	38.42
bool True	1
bool False	0
pyswip.Atom("carrot")	'carrot'
pyswip.Variable("Width")	Width
list ["string", 12, 12.34, Atom("jill")]	["string", 12, 12.34, 'jill']
Other value	str(value)

The placeholders are set using %p.

Example:

ids = [1, 2, 3]
joe = Atom("joe")
Prolog.assertz("user(%p,%p)", joe, ids)
list(Prolog.query("user(%p,IDs)", joe))