title: Nonetype object has no attribute 'items' when looping through a dictionary
body: <p>I have two dictionaries, one represents a player inventory and the other represents a dragon inventory. I'm trying to take the two dictionaries and combine them. Then display those two dictionaries as the player's new inventory. I have added my code below and I keep getting the following error.</p>
  
  <pre><code>Traceback (most recent call last):
    File "/Users/DakotaDickey/Documents/Python Projects /Examples/FantasyGameAddToInventory.py", line 38, in &lt;module&gt;
      displayInventory(inv)
    File "/Users/DakotaDickey/Documents/Python Projects /Examples/FantasyGameAddToInventory.py", line 27, in displayInventory
      for k, v  in inventory.items():
  AttributeError: 'NoneType' object has no attribute 'items'
  </code></pre>
  
  <p>my code:</p>
  
  <pre><code>#FantasyGameAddToInventory
  
  
  def addToInventory(inventory, addedItems):
      addedItemsdict = {} 
      for item in addedItems:
          x = addedItems.count(item)
          if item not in addedItemsdict:
              addedItemsdict[item] = 1
          else:
              addedItemsdict[item] = x
  
      for k, v in addedItemsdict.items():
          if k in inventory:
              x = inventory[k]
              inventory[k] = v + x
          else:
              inventory[k] = v
      inv = inventory           
      print(inv)
  
  def displayInventory(inventory):
      print('Inventory:')
      item_total = 0
  
      for k, v  in inventory.items():
          print(k,v)
          item_total = item_total + v
  
  
  
      print("Total number of items: " + str(item_total))
  
  inv = {'gold coin' : 42 , 'rope': 1}
  dragonLoot = ['gold coin', 'dagger' , 'gold coin', 'gold coin', 'ruby']
  inv = addToInventory(inv, dragonLoot)
  displayInventory(inv)
  </code></pre>
  
  <p>The output Im trying to produce is as follows. 
  Inventory:</p>
  
  <p>45 gold coin</p>
  
  <p>1 rope</p>
  
  <p>1 ruby</p>
  
  <p>1 dagger</p>
  
  <p>Total number of items: 48</p>