CODEWITHSUNDEEP
pythonlistdictionary
Roberto Demicheli
Roberto Demicheli

Reputation: 39

Python: Add a list to a dictionary

I want to add a list of items to an existing dictionary, but I am not getting the correct number of items. This is my code.

d = {'rope': 1, 'torch': 6, 'gold coin': 3, 'dagger': 1, 'arrow': 12}

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

displayInventory(d)

print()

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

def addToInventory(inventory, add):
    new= dict.fromkeys(add, 1)
    for k, v in new.items():
        inventory[k] = v

z = addToInventory(d, dragonLoot)

displayInventory(d)

The expected output should be this

Inventory:
1 rope
6 torch
5 gold coin
2 dagger
12 arrow
1 ruby
Total number of items: 27

Upvotes: 0

Views: 179

Answers (3)

seymourgoestohollywood
seymourgoestohollywood

Reputation: 1167

Consider restructuring and using a Counter like below:

from collections import Counter

inventory = Counter({'rope': 1, 'torch': 6, 'gold coin': 3, 'dagger': 1, 'arrow': 12})


def displayInventory():

    print('Inventory:')

    for k, v in inventory.items():
        print(v, k)

    print(f'Total number of items: {sum(inventory.values())}')


displayInventory()

dragonLoot = ['gold coin', 'dagger', 'gold coin', 'ruby']
print('--Picked up loot!')

inventory.update(dragonLoot)

displayInventory()

Gives:

Inventory:
1 rope
6 torch
3 gold coin
1 dagger
12 arrow
Total number of items: 23
--Picked up loot!
Inventory:
1 rope
6 torch
5 gold coin
2 dagger
12 arrow
1 ruby
Total number of items: 27

This also means that if you can safely check the inventory for items not already in there like:

print(inventory['diamond'])

which gives:

0

(a normal dict would raise a KeyError).

Upvotes: 1

Gloweye
Gloweye

Reputation: 1408

You might want to use a collections.Counter. If you use it, your could would look like this:

d = Counter({'rope': 1, 'torch': 6, 'gold coin': 3, 'dagger': 1, 'arrow': 12})
loot = ['gold coin', 'dagger', 'gold coin', 'ruby']
d.update(loot)
print(d)
# Counter('rope': 1, 'torch': 6, 'gold coin': 5, 'dagger': 2, 'arrow': 12, 'ruby':1)

Upvotes: 0

Encrypted
Encrypted

Reputation: 188

This is because the dict.fromkeys(add, 1) does something else then you think:

dragonLoot = ['gold coin', 'dagger', 'gold coin', 'ruby']
>>> dict.fromkeys(dragonLoot, 1)
{'gold coin': 1, 'ruby': 1, 'dagger': 1}

So it does not count the occurences.

I would change the addToInventory function to this:

def addToInventory(inventory, add):
    for k in add:
        inventory[k] = inventory.get(k, 0) + 1

So you loop over the items you found and add it to your inventory

Upvotes: 1

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