Correct some interface bugs regarding potential user input

resources/interface.py

@@ -158,30 +158,33 @@ class UserInterface():
         print('')
 
         # Attempt to set file contents as new item set.
-        with open(user_input, 'r') as file:
-            # Read in file.
-            json_data = json.load(file)
-
-            # Check that JSON data is formatted in way we expect.
-            if self._knapsack_algorithm.set_item_set(json_data):
-                # Successfully set JSON data as new item set.
-                print('Successfully set new Item Set from JSON data.')
-                self._knapsack_algorithm.display_item_set()
-            else:
-                # Validation failure.
-                print('Failed to validate file contents for Item Set.')
+        try:
+            with open(user_input, 'r') as file:
+                # Read in file.
+                json_data = json.load(file)
+
+                # Check that JSON data is formatted in way we expect.
+                if self._knapsack_algorithm.set_item_set(json_data):
+                    # Successfully set JSON data as new item set.
+                    print('Successfully set new Item Set from JSON data.')
+                    self._knapsack_algorithm.display_item_set()
+                else:
+                    # Validation failure.
+                    print('Failed to validate file contents for Item Set.')
+        except FileNotFoundError:
+            print('Failed to locate file "{0}".'.format(user_input))
 
     def add_to_item_set(self):
         """
         Adds new "Item" to "Item Set" by manual input.
         """
-        print('Enter a benefit amount (must be a positive integer):')
+        print('Enter Item "Benefit" amount (must be a positive integer):')
 
         # Get user's input.
         benefit_input = input()
         print('')
 
-        print('Enter a cost amount (must be a positive integer):')
+        print('Enter Item "Cost" amount (must be a positive integer):')
 
         # Get user's input.
         cost_input = input()
@@ -221,4 +224,8 @@ class UserInterface():
         """
         Solves knapsack with current problems and displays result to user.
         """
-        self._knapsack_algorithm.calculate_fractional_knapsack()
+        self._knapsack_algorithm.display_max_weight()
+        self._knapsack_algorithm.display_item_set()
+        results = self._knapsack_algorithm.calculate_fractional_knapsack()
+        print('Optimal backpack contents, by weight of each item to take:')
+        print(results)

resources/knapsack.py

@@ -38,8 +38,13 @@ class FractionalKnapsackAlgorithm():
         """
         # First validate item set.
         if self.validate_item_set(item_set):
-            # Validation passed. Set values.
-            self._item_set_ = item_set
+            # Validation passed. First clear item set.
+            self.clear_item_set()
+
+            # Now add each item to new set.
+            for item in item_set:
+                self._add_item_to_item_set(item)
+
             self._items_populated_ = True
             return True
         else:
@@ -91,20 +96,35 @@ class FractionalKnapsackAlgorithm():
 
     def add_item_to_item_set(self, item):
         """
-        Adds dictionary item to item set.
+        Validates dictionary item. On success, calls internal function to add to item set.
         :param item: Potential new item to add to "item set".
         :return: Bool indicating if item was successfully added or not.
         """
         # First validate that item matches requirements.
         if self.validate_item_set([item]):
             # Validation success.
-            self._item_set_.append(item)
-            self._items_populated_ = True
+
+            self._add_item_to_item_set(item)
             return True
         else:
             # Validation failed. Item not added.
             return False
 
+    def _add_item_to_item_set(self, item):
+        """
+        Adds item to item set.
+        :param item: Validated item.
+        """
+        # Clean item (Just because values were parsable as int's doesn't mean they currently are).
+        cleaned_item = {
+            'benefit': int(str(item['benefit']).strip()),
+            'cost': int(str(item['cost']).strip()),
+        }
+
+        # Add to item set.
+        self._item_set_.append(cleaned_item)
+        self._items_populated_ = True
+
     def set_max_weight(self, max_weight):
         """
         Sets upper bound to limit algorithm choices.