Incrementing list values

Question

I have a player template that I am copying, setting a field, and then appending the updated template to a new list.

player_template = {
    "player": "",
    "hand": [
        {0 :
            {
                "cards_in_hand": [],
                "cards_taken": []
            }
        }
    ]
}

However, when I go to do a range loop to create multiple players, it only creates the last player multiple times.

for i in range(4):
        p["player"] = i
        players.append(p)

Output:

[
    {
        'player': 3,
        'hand': [
            {
                0: {
                    'cards_in_hand': [],
                    'cards_taken': []
                }
            }
        ]
    },
    {
        'player': 3,
        'hand': [
            {
                0: {
                    'cards_in_hand': [],
                    'cards_taken': []
                }
            }
        ]
    },
    {
        'player': 3,
        'hand': [
            {
                0: {
                    'cards_in_hand': [],
                    'cards_taken': []
                }
            }
        ]
    },
    {
        'player': 3,
        'hand': [
            {
                0: {
                    'cards_in_hand': [],
                    'cards_taken': []
                }
            }
        ]
    }
]

I've tried range(start, stop, step) , but it also produces the same results. How can I get the output to be player 1, player 2, etc.?

Answer 1

Currently you're overriding the previous player with each iteration. This is because dictionaries are mutable objects and you're poinging to the same one.

You need to deep-copy the mapping that represents a player:

import copy

for i in range(4):
    p["player"] = i
    players.append(copy.deepcopy(p))

I've used copy.deepcopy but you can do this manually if you want.

A better way would be to use an actual class to reperesent a Player .