cannot understand why these two codes dont have the same output

input1 :

for i in range(5):
    lst = [0,0,0,0,0]
    lst[i] = 1
    print(lst)

output1 :

1, 0, 0, 0, 0
0, 1, 0, 0, 0
0, 0, 1, 0, 0
0, 0, 0, 1, 0
0, 0, 0, 0, 1

input2 :

mainlst = [0,0,0,0,0]
for i in range(5):
    templst = mainlst
    templst[i] = 1
    print(templst)

output2 :

1, 0, 0, 0, 0
1, 1, 0, 0, 0
1, 1, 1, 0, 0
1, 1, 1, 1, 0
1, 1, 1, 1, 1

Why does assigning a value, to a variable, 1) as a list, and 2) as a variable(whose value is the same as the list), not have the same output
i expected the two to give the same output

>Solution :

In the second example you’re referencing the mainlst every time. If you change your code to:

mainlst = [0,0,0,0,0]
for i in range(5):
    templst = mainlst.copy()
    templst[i] = 1
    print(templst)

You’ll get the same results. Look up more about python arrays and deep vs shallow copies.

https://realpython.com/copying-python-objects/