can anyone help me understanding this python multidimensional array problem.

Question

x = [[0]*2]*2
x[0][0]=1
then if i print x,why does it shows [[1,0],[1,0]] instead of [[1,0],[0,0]]

Answer 1

When you create a list with *, you effectively add REFERENCE to the list and not copies. At example:

l= [0,0]*2
# now l will be [[0,0],[0,0]
# but either items are SAME
# object then if you modify one
# then other one will be modified
# also

l[0][0]= 1

# At thid point you edits
# first item of first item of
# l BUT because it contains
# two items that ARE SAME OBJECT
# you will edit also the first
# item of second item of
# l

In practice when you do
l= [i1,i2 ... im]*n

its almost like

tmp= [i1, i2 .... im]
l= [tmp, tmp ... tmp] # n times

Answer 2

Are you sure that the code and the output is like you writed?

Answer 3

my mistake,edited to complete problem