Python list and for loop

Question

I'm expecting this code to print spade:A spade:2 and so on until heart:K.
But it only does heart:A to heart:K.
How should I do it?

symbols = ["spade", "clover", "diamond", "heart"]
numbers = ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q",       "K"]
cards = {}

for num in numbers:
    for symbol in symbols:
        cards[num] = symbol

print cards

Answer 1

Use your itertools toolbox

import itertools

symbols = ["spade", "clover", "diamond", "heart"]
numbers = ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q",       "K"]

combinations = itertools.product(symbols, numbers)

cards = ["{}:{}".format(suit, rank) for suit,rank in combinations]

This will give you the list:

['spade:A',
 'spade:2',
 'spade:3',
 'spade:4',
 'spade:5',
 'spade:6',
 'spade:7',
 'spade:8',
 'spade:9',
 'spade:10',
 'spade:J',
 'spade:Q',
 'spade:K',
 'clover:A',
 'clover:2',
 'clover:3',
 'clover:4',
 'clover:5',
 'clover:6',
 'clover:7',
 'clover:8',
 'clover:9',
 'clover:10',
 'clover:J',
 'clover:Q',
 'clover:K',
 'diamond:A',
 'diamond:2',
 'diamond:3',
 'diamond:4',
 'diamond:5',
 'diamond:6',
 'diamond:7',
 'diamond:8',
 'diamond:9',
 'diamond:10',
 'diamond:J',
 'diamond:Q',
 'diamond:K',
 'heart:A',
 'heart:2',
 'heart:3',
 'heart:4',
 'heart:5',
 'heart:6',
 'heart:7',
 'heart:8',
 'heart:9',
 'heart:10',
 'heart:J',
 'heart:Q',
 'heart:K']

Answer 2

The problem is that you are not iterating the right way and thus you are not appending in the list. The right way to do it is

symbols = ["spade", "clover", "diamond", "heart"]
numbers = ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q",         "K"]
cards = []

for j in range(len(symbols)):
    for i in range(len(numbers)):
       cards.append(str(symbols[j]+':'+str(numbers[i])))

print cards

with output:

['spade:A', 'spade:2', 'spade:3', 'spade:4', 'spade:5', 'spade:6', 'spade:7',  'spade:8', 
'spade:9', 'spade:10', 'spade:J', 'spade:Q', 'spade:K', 'clover:A', 'clover:2',
'clover:3', 'clover:4', 'clover:5', 'clover:6', 'clover:7', 'clover:8', 'clover:9',
'clover:10', 'clover:J', 'clover:Q', 'clover:K', 'diamond:A', 'diamond:2', 'diamond:3',
'diamond:4', 'diamond:5', 'diamond:6', 'diamond:7', 'diamond:8', 'diamond:9', 'diamond:10',
'diamond:J', 'diamond:Q', 'diamond:K', 'heart:A', 'heart:2', 'heart:3', 'heart:4',
'heart:5', 'heart:6', 'heart:7', 'heart:8', 'heart:9', 'heart:10', 'heart:J', 'heart:Q', 'heart:K']

Made with Ipython Notebook in python 2.7

Hope it helps.

Answer 3

You are iterating the symbols just fine but when you are going over the numbers in the second loop, you are actually replacing the values set by the previous loop hence you only have values from the last loop left and everything is replaced. This means cards["A"] value is set 4 times in the loop and the last for the "heart" is retained. The same thing is happening for all the other indexes.