[nfbcs] Can anyone help me understand what I'm doing wrong here?

[Lanie Molinar]

Hi, everyone. I'm learning Python 3 from a book called "Automate the 
Boring Stuff with Python", and I just learned about dictionaries. I'm 
now trying the practice projects at the end of the lesson, and I thought 
I understood what I was doing until I got an error when I ran my code. 
The project description is below. There are two in this lesson, but 
they're short and one builds on the other, so I'm pasting both here.

  Fantasy Game Inventory
You are creating a fantasy video game. The data structure to model the 
player’s inventory will be a dictionary where the keys are string values 
describing the item in the inventory and the value is an integer value 
detailing how many of that item the player has. For example, the 
dictionary value {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1, 
'arrow': 12} means the player has 1 rope, 6 torches, 42 gold coins, and 
so on.
Write a function named displayInventory() that would take any possible 
“inventory” and display it like the following:

Inventory:
12 arrow
42 gold coin
1 rope
6 torch
1 dagger
Total number of items: 62
Hint: You can use a for loop to loop through all the keys in a dictionary.

# inventory.py
stuff = {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1, 'arrow': 12}

def displayInventory(inventory):
     print("Inventory:")
     item_total = 0
     for k, v in inventory.items():
         # FILL IN THE CODE HERE
     print("Total number of items: " + str(item_total))

displayInventory(stuff)
  List to Dictionary Function for Fantasy Game Inventory
Imagine that a vanquished dragon’s loot is represented as a list of 
strings like this:

dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']
Write a function named addToInventory(inventory, addedItems), where the 
inventory parameter is a dictionary representing the player’s inventory 
(like in the previous project) and the addedItems parameter is a list 
like dragonLoot. The addToInventory() function should return a 
dictionary that represents the updated inventory. Note that the 
addedItems list can contain multiples of the same item. Your code could 
look something like this:

def addToInventory(inventory, addedItems):
     # your code goes here

inv = {'gold coin': 42, 'rope': 1}
dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']
inv = addToInventory(inv, dragonLoot)
displayInventory(inv)
The previous program (with your displayInventory() function from the 
previous project) would output the following:

Inventory:
45 gold coin
1 rope
1 ruby
1 dagger

Total number of items: 48


My code is below:

stuff = {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1, 'arrow': 12}

def displayInventory(inventory):
     print("Inventory:")
     item_total = 0
     for k, v in inventory.items():
         print(v, k)
         item_total += v
     print("Total number of items: " + str(item_total))

displayInventory(stuff)

def addToInventory(inventory, addedItems):
     for i in addedItems:
         inventory.setdefault(i, 1)
         if i in inventory:
             inventory[i] += 1

inv = {'gold coin': 42, 'rope': 1}
dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']
inv = addToInventory(inv, dragonLoot)
displayInventory(inv)


The exception I get says:
   Message=AttributeError("'NoneType' object has no attribute 'items'")
Source=c:\users\lanie\source\repos\pythonpractice\fantasygameinventory\fantasygameinventory.py
   StackTrace:
   File 
"c:\users\lanie\source\repos\pythonpractice\fantasygameinventory\fantasygameinventory.py", 
line 6, in displayInventory
     for k, v in inventory.items():
   File 
"c:\users\lanie\source\repos\pythonpractice\fantasygameinventory\fantasygameinventory.py", 
line 22, in <module>
     displayInventory(inv)
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\pydevd\_pydev_imps\_pydev_execfile.py", 
line 25, in execfile
     exec(compile(contents+"\n", file, 'exec'), glob, loc)
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\pydevd\pydevd.py", 
line 1035, in run
     pydev_imports.execfile(file, globals, locals)  # execute the script
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\pydevd\pydevd.py", 
line 1628, in main
     globals = debugger.run(setup['file'], None, None, is_module)
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\_main.py", 
line 101, in _run
     raise
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\_main.py", 
line 47, in run_file
     run(argv, addr, **kwargs)
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\packages\ptvsd\debugger.py", 
line 36, in debug
     run(address, filename, *args, **kwargs)
   File "c:\program files (x86)\microsoft visual 
studio\preview\community\common7\ide\extensions\microsoft\python\core\ptvsd_launcher.py", 
line 111, in <module>
     vspd.debug(filename, port_num, debug_id, debug_options, run_as)

It seems to think my inventory dictionary has the none type, and I don't 
understand why. Can anyone see what I'm doing wrong? Thanks.