Why can I use a list index as an indexing variable in a for loop? [duplicate]

Answer 1

The left expression of a for loop statement gets assigned with each item in the iterable on the right in each iteration, so

for n in a:
    print(n)

is just a fancy way of doing:

for i in range(len(a)):
    n = a[i]
    print(n)

Likewise,

for a[-1] in a:
  print(a[-1])

is just a fancy way of doing:

for i in range(len(a)):
    a[-1] = a[i]
    print(a[-1])

where in each iteration, the last item of a gets assigned with the next item in a, so when the iteration finally comes to the last item, its value got last assigned with the second-last item, 2.