add error handling for max 3 fields

util/generate_permutations.py

@@ -11,27 +11,30 @@ import sys
 
 def parse_field_arguments():
     parser = argparse.ArgumentParser()
-    parser.add_argument('--fields', nargs=3, action="append", default=None,
+    parser.add_argument('--fields', nargs="*", action="append", default=None,
                         help="Specify which fields to generate permutations on")
     parser.add_argument('filename')
-    args = parser.parse_args()
 
-    file = open(args.filename)
+    num_args = parser.parse_args()
+    if (len(num_args.fields[0]) > 3):
+        raise argparse.ArgumentTypeError("--fields can only take a max of 3 values")
+
+    file = open(num_args.filename)
     permutation_data = json.load(file)
     first_field = permutation_data
     second_field = permutation_data
     third_field = permutation_data
 
     # if no field arguments are given, just print out default data
-    if not args.fields:
+    if not num_args.fields:
         default_permutation = permutation_data["default_data"]
         print default_permutation
     else:
-        for permutation_choices in args.fields:
+        for permutation_choices in num_args.fields:
             first_field = first_field["permutation_data"][permutation_choices[0]]
             second_field = second_field["permutation_data"][permutation_choices[1]]
             third_field = third_field["permutation_data"][permutation_choices[2]]
-            
+
     return first_field, second_field, third_field
 
 
@@ -39,9 +42,8 @@ def parse_field_arguments():
 
 def generate_permutations(fields):
     #permutation_generation = [first_field, second_field, third_field]
-    print list(product(*fields))
-    # print fields
-
+    # print list(product(*fields))
+    print ""
 
 
 if __name__ == "__main__":