US Map Coloring problem using Constraint Satisfaction

Question

I have a list of states:

    variables = [\'WA\', \'ID\', \'OR\', \'NV\', \'CA\', \'ND\', 
    \'MT\', \'UT\', \'AZ\', \'WY\', \'CO\', \'NM\', \'SD\', \'NE\',