Question on loops and append method.

Question

L, D = [], []
for i in range(3):
D.append(i)
L.append(D)
print(L)

output : [[0,1,2],[0,1,2],[0,1,2]]

I thought the output is [[0],[0,1],[0,1,2]]

Can anyone please explain me this?

Answer 1

Because lists are mutable. Every time you append to D you are effectivly changing EVERY occurence of D. What youre doing works, you can test it by printing L INSIDE the for loop.

At the end, L contains 3 lists (D) with all the same values, wich is why its all the same

Answer 2

Slick
Ahhg! Thanks a lot. 'Lists are mutable' The key sentence.

A lot of thanks.

Answer 3

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥
Thanks a lot, buddy.