根据值更新字典键

Question

I have the following dictionary:

players = {'Roger': ['player1', 'dA'], 'Luka': ['player2', 'sK']}. 

I want to update the key that contains 'player2' , but I can't update players [Luka] because 'player2' is not always Luka . How can I select keys linked to 'player2' ?

(for those wondering, dA = Ace of Diamonds , sK = King of Spades . These values will also be different every time).

Edit: Here's the part of my code: (It won't run because I left out a lot of clutter)

qPlayers = 2  #Amount of players
def game(qPlayers):
    players[nr]["value"].append(new_card)
    deal_to =[]
    for player in players:
        deal_to.append(player)
    deal(qPlayers,deck,players,deal_to)

def setup(qPlayers):
    playerhands = []
    for x in range(1,qPlayers+1):
        player = {}
        player["name"] = input("Enter your name, player {}\n>>>".format(x))
        playerhands.append(player)
    return playerhands      


def deal(qPlayers,deck,players,deal_to):
    nr = -1
    for player in deal_to:
        nr +=1
        new_card = getCard(deck)   #getCard produces a random card like sA, k9, cQ

Answer 1

You can keep track of which key in the dict contains your player2 value, or else you will have to iterate through the dict until you find a key that does. If you frequently need to search based on something internal to the value , you may want to reconsider the data structure you are using to store this data.

def findKeyWithValue(value):
    for playerName, playerData in players.items():
        if value in playerData:
            # your code here

Answer 2

You have two options here:

1. Search through the entire directory, checking for the value which contains 'player2'. This ends up being inefficient, and makes the dictionary structure somewhat useless.

2. Use a list instead of a dictionary, and model your data accordingly, similar to the example below.

An advantage of this data structure is that you don't need the redundant player1 / player2 identifiers, since the list index provides that implicitly. To reference player2 you'd take the second element from the list ( players[1] since indexing starts at 0).

players = [
    {'Name' : 'Roger', 'Value' : 'dA'},
    {'Name' : 'Luka', 'Value' : 'sK'}
]

Answer 3

You can iterate the dictionary to find the key to update. dict.iteritems() will do that job in python 2.7.

players = {'Roger': ['player1', 'dA'], 'Luka': ['player2', 'sK']}

for key, value in players.iteritems():
    if value[0] == "player2":
        players[key][1] = "sQ"

print players