[SOLVED] Creating relations with unify and regular expression

Creating relations with unify and regular expression

I'm trying to create a relation with unify for example:

Boy(Mike) --> Mike is a boy

Girl(Lisa) --> Lisa is a girl

isSister(Mike,Lisa) --> Lisa is Mike's sister

and this is my code:

from fact import Fact
from logic import get, unify, var

from itertools import chain 
import regex as re


facts = {}

pattern = r"(\w+)\((?:([^,\)]+)\,(?:([^,\)]+)))+\)\.?"

rule = input('Ingrese un hecho o consulta:')
while rule != '!':
  match = re.match(pattern, rule)
  print(match)
  name = match.captures(1)[0]
  argument1 = match.captures(2)
  argument2 = match.captures(3)
  if rule.endswith('.'):
    if not name in facts:
      facts[name] = Fact()
    facts[name].append(argument1[0])
    facts[name].append(argument2[0])
  else:
    X = var()
    Y = var()
    for _ in facts[name](X,Y): print(get(X),get(Y))
  rule = input('Ingrese un hecho o consulta:')

What I want, is that when I ask for isSister(?,Lisa), it returns Mike. This is what I get:

Traceback (most recent call last): File "main.py", line 17, in name = match.captures(1)[0] AttributeError: 'NoneType' object has no attribute 'captures'

Solution

match returns None if there is no match, and this appears to happen somewhere in your while loop. You'll need to handle this case somehow, either by:

if match == None:
    # handle

or:

try:
   name=match.captures(1)[0]
except AttributeError as e:
    # handle

It's up to you to pick the handling that fits your solution, but these are the two patterns I generally go for. There are others I'm sure, but I would suggest starting here.