Creating a List - Creating one more level of list than wanted

Question

I am able to successfully add to a list called donnes elements from a list called liste_dominos. However, it seems like I'm creating an extra level in the list.

While printing donnes, instead of having this output :

[[[5, 3], [6, 3], [2, 0], [4, 2], [2, 2], [6, 6]]], [[[2, 1], [6, 5], [6, 4], [3, 0], [3, 3], [3, 2]]]

I would get :

[[[[5, 3], [6, 3], [2, 0], [4, 2], [2, 2], [6, 6]]], [[[2, 1], [6, 5], [6, 4], [3, 0], [3, 3], [3, 2]]]]

Thus if I get the list of each player... instead of having this output : [[5, 3], [6, 3], [2, 0], [4, 2], [2, 2], [6, 6]]

I would get : [[[5, 3], [6, 3], [2, 0], [4, 2], [2, 2], [6, 6]]]

The list donnes should be formated as thus [[],[]]. Each element represents a player and in its sublist, the list of dominos they hold.

Here's the code.

import random

liste_dominos = [[6, 6], [6, 5], [6, 4], [6, 3], [6, 2], [6, 1], [6, 0], [5, 5], [5, 4], [5, 3], [5, 2], [5, 1], [5, 0], [4, 4], [4, 3], [4, 2], [4, 1], [4, 0], [3, 3], [3, 2], [3, 1], [3, 0], [2, 2], [2, 1], [2, 0], [1, 1], [1, 0], [0, 0]]
random.shuffle(liste_dominos)
no_players = 2
if int(no_players) == 2:
    donnes = [[] for i in range(int(no_players))]
    for x in range(no_players):
        donnes[x].append(liste_dominos[:6])
        del liste_dominos[:6]
    print(donnes[0])
    print(donnes[1])
    print(donnes)

The print is only there as an indication whether I get the correct result or not. I will be later on using the donnes list to perform other operations and thus need to get it in the aforementioned format.

score 3 · Accepted Answer · answered Mar 31 '18 at 17:53

even tho there are better approaches, what is happening is that you are appending to the list what is returned from liste_dominos[:6] as it's, and this is basically a list of the elements contained in that range which are a list returning in fact [ [...],..,[...]]

Using extend to append the inner elements of the list solves this:

import random

liste_dominos = [[6, 6], [6, 5], [6, 4], [6, 3], [6, 2], [6, 1], [6, 0], [5, 5], [5, 4], [5, 3], [5, 2], [5, 1], [5, 0], [4, 4], [4, 3], [4, 2], [4, 1], [4, 0], [3, 3], [3, 2], [3, 1], [3, 0], [2, 2], [2, 1], [2, 0], [1, 1], [1, 0], [0, 0]]
random.shuffle(liste_dominos)
no_players = 2
if int(no_players) == 2:
    donnes = [[] for i in range(int(no_players))]
    for x in range(no_players):

        # Changed to extend instead of append
        # It can be changed to += also
        donnes[x].extend(liste_dominos[:6])
        del liste_dominos[:6]

    print(donnes[0])
    > [[1, 0], [6, 5], [4, 3], [5, 2], [6, 3], [5, 5]]

    print(donnes[1])
    > [[5, 1], [3, 2], [4, 1], [2, 1], [3, 0], [2, 2]]

    print(donnes)
    > [[[1, 0], [6, 5], [4, 3], [5, 2], [6, 3], [5, 5]], [[5, 1], [3, 2], [4, 1], [2, 1], [3, 0], [2, 2]]]

That works exactly as intended. Thank you very much. – Nore Mar 31 '18 at 18:09 — Nore, Mar 31 '18 at 18:09

score 1 · Answer 2 · answered Mar 31 '18 at 18:09

You are using append() when you actually want extend().

append: Appends object at end.

x = [1, 2, 3]
x.append([4, 5])
print (x)

gives you: [1, 2, 3, [4, 5]]

extend: Extends list by appending elements from the iterable.

x = [1, 2, 3]
x.extend([4, 5])
print (x)

gives you: [1, 2, 3, 4, 5]

You want to do

donnes[x].extend(liste_dominos[:6])

Original extend vs. append answer here

score 0 · Answer 3 · answered Mar 31 '18 at 18:08

You could make same job much easier with list comprehension

import random
liste_dominos = [[6, 6], [6, 5], [6, 4], [6, 3], [6, 2], [6, 1], [6, 0], [5, 5], [5, 4], [5, 3], [5, 2], [5, 1], [5, 0], [4, 4], [4, 3], [4, 2], [4, 1], [4, 0], [3, 3], [3, 2], [3, 1], [3, 0], [2, 2], [2, 1], [2, 0], [1, 1], [1, 0], [0, 0]]
random.shuffle(liste_dominos)
no_players = 2
res = [liste_dominos[i*6:(i+1) * 6] for i in range(no_players)]
res
Out[8]: 
[[[2, 2], [4, 1], [1, 1], [6, 0], [4, 2], [5, 3]],
 [[3, 3], [0, 0], [5, 1], [3, 2], [5, 5], [5, 2]]]

Creating a List - Creating one more level of list than wanted

3 Answers3