For loops and list reassignment

Question

I encountered the following code during a challenge:
*What is the output*
A = [1, 2, 3, 4, 1]
for n in A:
A[n] = 0
print(A)

# output is [0, 0, 3, 0, 1]
After looking at the code and the answer and putting it into playground, I was still unsure of why this was the output. I think it has something to do with the for loop, but if someone could clarify I would be grateful. Thanks!

Answer 1

Pretty hard to figure that out in the limited time you have in a challenge

Answer 2

A[n] = 0 is a list slice which seems to do the following

A = [1,2,3,4,1]
A[n] == A[0] iteration => A[1] slice =2

A = [1,0,3,4,1]
A[n] == A[1] iteration => A[0] slice =1

A = [0,0,3,4,1]
A[n] == A[2] iteration => A[3] slice = 4

A = [0,0,3,0,1]
A[n] == A[3] iteration => A[0] slice = 0

A[0,0,3,0,1]
A[n] == A[4] iteration => A[1] slice = 0

Final result:
A = [0,0,3,0,1]

Answer 3

Try running your code like this to see the iterations of A, it may help you understand.

A = [1, 2, 3, 4, 1]
for n in A:
A[n] = 0
print(A)

Answer 4

Thank you, your explanation helped a lot.