Initializing Multi-Dimensional List Python Reference Issue

Asked May 15 '17 at 05:22

Active May 15 '17 at 05:29

Viewed 52 times

If I create a two dimensional matrix as follows:

n = 5
m = 5
l = [[0] * n] * m
l[0][0] = 1
print(l)

will output:

[[1, 0, 0, 0, 0],
 [1, 0, 0, 0, 0],
 [1, 0, 0, 0, 0],
 [1, 0, 0, 0, 0],
 [1, 0, 0, 0, 0]]

Why? why are all the sub-lists first elements being set to 1??

edited May 15 '17 at 05:29

Yu Hao

asked May 15 '17 at 05:22

lonel

http://stackoverflow.com/questions/7745562/appending-to-2d-lists-in-python – Praveen May 15 '17 at 05:30
`l = [[0] * n for i in range(m)]` – Praveen May 15 '17 at 05:31

0 Answers0