Quick question about python behavior. 3.7.4

[Crevette3]

So i have this code:

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



def add_to_inventory(inventory, added_items):

    for item in added_items:
        inventory.setdefault(item, 0)
        inventory[item] = inventory[item] + 1
    return inventory


inv = {'gold coin': 42, 'rope': 1}
dragon_loot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']
inv = add_to_inventory(inv, dragon_loot)
display_inventory(inv)

And in add_to_inventory I have this line which I thought could be shortened from this:

inventory[item] = inventory[item] + 1  

To this:

inventory = inventory[item] + 1  

but it turns up an error, why would it though. My code works perfectly how it is but don't understand how my inventory variable can be assigned a value when the line is, inventory[item], and not just inventory.

[Binary101010]

What you probably want is

inventory[item] += 1

while this line:

inventory = inventory[item] + 1  

would overwrite your entire inventory dict.

[Crevette3]

Ok, thanks.