Here is my code:

```
inv = {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1}

def display_inventory(inventory):
    #inv = {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1}
    print("Inventory:")
    for key, value in inv.items():
            print value, key
    print("")
    print "Number of items is: ",
    print (sum(inv.values())),

def add_to_inventory(inventory, added_items):
    dragon_loot_dict = dict.fromkeys(added_items, 1)
    #print(dragon_loot_dict)
    inventory=dict(inventory.items()+ dragon_loot_dict.items())
    print(inventory)

dragon_loot = ['gold coin', ' dagger', 'gold coin', 'gold coin', 'ruby']

add_to_inventory(inv, dragon_loot)

```

I'v just started learning Python. When I'm adding loot from monster to my main inventory, values from main inventory is changing to values from monster inventory.

How can I add values of the same items e.g., `gold coin`?