could someone please explain the answer briefly

Question

a=[0,1,2,3]
for a[-1] in a:
print(a[-1])

Answer 1

for x in y means:

'Please let x be each element of y consecutively.'

This is comparable to you just writing:

x = y[0]
x = y[1]
and so forth.

Now for a[-1] means that instead of a variable x, the last slot of a is taken as the 'vessel' where each element will be stored.

Answer 2

Thank you HonFu