Python for loop and lists

Question

I have the following in code; which I forgot where I got it or what's it called (I'm new to Python):

deck = [Card(x, y) for x in cards for y in suits]

From the above code, I am trying to create multiple decks into a list, so that the user inputs the number of decks. I have been trying to do it like this:

decks = 2
i = 0
while i < decks:
    deck = [Card(x, y) for x in cards for y in suits]
    i += 1

But that just overwrites the current deck variable. I also tried:

decks = 2
deck = []
i = 0
while i < decks:
    deck.append(Card(x, y) for x in cards for y in suits)
    i += 1

But I only get <generator object <genexpr> at 0x04562C30> and <generator object <genexpr> at 0x04562BF0> as output when I print the contents of the deck. How exactly do I achieve what I want and how do the two for loops work in the creation of the list?

I tried the following to iterate over the members of the list; doesn't work:

for x in deck:
    for j in x:
        print(str(deck[x][j]))

That is called list comprehension.

Mohit Motwani
– Mohit Motwani

2018-11-20 12:36:18 +00:00
Commented Nov 20, 2018 at 12:36 — Mohit Motwani
– Mohit Motwani, Commented Nov 20, 2018 at 12:36
deck.append([...])?

Arnav Borborah
– Arnav Borborah

2018-11-20 12:37:27 +00:00
Commented Nov 20, 2018 at 12:37 — Arnav Borborah
– Arnav Borborah, Commented Nov 20, 2018 at 12:37

Mehrdad Pedramfar · Accepted Answer · 2018-11-20 13:08:25Z

12

Try this:

deck.append([Card(x, y) for x in cards for y in suits])

This will be a list of lists. but I think all of the items will be the same in that list.

EDIT:

for x in deck:
    for j in x:
        print(j) # or do what you want, j is that inner element

edited Nov 20, 2018 at 13:08

answered Nov 20, 2018 at 12:38

Mehrdad Pedramfar

11.1k4 gold badges43 silver badges61 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

EInherjar Over a year ago

How do I iterate over the members of the inner lists? Do I need two loops for that?

Mehrdad Pedramfar Over a year ago

Yes, you need two loop for accessing all of them but individually you can deck[i][j]. i and j will be the Integer indexes.

Mehrdad Pedramfar Over a year ago

You can iterate over them and flat the like this: [member for l in deck for member in l]

EInherjar Over a year ago

Could you edit the answer to include how to iterate over the members please. I have edited my question what I tried and it doesn't work.

Mehrdad Pedramfar Over a year ago

sure,just print(j) instead of str(deck[x][j])

|

Arnav Borborah · Accepted Answer · 2018-11-20 12:39:17Z

2

You should change this,

deck.append(Card(x, y) for x in cards for y in suits)

into this:

deck.append([Card(x, y) for x in cards for y in suits])

Instead of appending a generator object each iteration of the list comprehension, which is what the first line does, the second line stores the data in a list and then appends it.

answered Nov 20, 2018 at 12:39

Arnav Borborah

11.8k8 gold badges51 silver badges94 bronze badges

Comments

Rahul Chawla · Accepted Answer · 2018-11-20 13:52:24Z

1

Just adding a comprehension version for the sake of completion.

decks = 2

deck = [[(x,y) for x in cards for y in suits] for i in range(decks)]

answered Nov 20, 2018 at 13:52

Rahul Chawla

1,08810 silver badges16 bronze badges

2 Comments

EInherjar Over a year ago

Would this create a single list or two lists in a list?

Rahul Chawla Over a year ago

2 Lists in a list.

Collectives™ on Stack Overflow

Python for loop and lists

3 Answers 3

7 Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

7 Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related