Python : List elements are connected, how to separate

Question

def list():
    mylist = [[0,0,0,0]]*3
    mylist[1][2] = 8013
    print(mylist)

Output:

[[0,0,8013,0],[0,0,8013,0],[0,0,8013,0]]

Wanted output:

[[0,0,0,0],[0,0,8013,0],[0,0,0,0]]

How do I fix this?

@inspectorG4dget Could you please link to the duplicate thread? I tried searching, but couldn't find anything. — Frank Vel, Oct 11 '15 at 19:55
Refresh the page. You should see the duplicate linked in an edit to your post — inspectorG4dget, Oct 11 '15 at 19:57
@inspectorG4dget Ah thanks! Even that one is marked as possible duplicate... Should I just delete this, or let it stay so others have a better chance of searching and finding the problem? — Frank Vel, Oct 11 '15 at 20:00

score 2 · Accepted Answer · answered Oct 11 '15 at 19:47

2

Use eval on repr.

mylist = eval(repr([[0,0,0,0]]*3))

or use list comp to produce the list

mylist = [[0,0,0,0] for _ in range(3)]

answered Oct 11 '15 at 19:47

Nizam Mohamed

8,751
24
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score 1 · Answer 2 · answered Oct 11 '15 at 19:51

1

Use mylist = [[0 for _ in xrange(4)] for _ in xrange(3)]

Using * will cause Python to use the same object for the whole list, and that's why when you change any one of the element in the list, you are changing the rest of them.

answered Oct 11 '15 at 19:51

user1537085

404
5
18

Python : List elements are connected, how to separate

2 Answers2