The primary aim of the for statement is to traverse a list:

for s in ['a', 'b', 'c']:
    print(s), # a b c

In this example, the loop variable s is successively assigned to one element of the list. Notice that the loop variable is available after the loop has terminated. This may sometimes be useful; refer, for instance, the example in section Controlling the flow inside the loop.

One of the most frequent uses of a for loop is to repeat a given task a defined number of times, using the function range  (refer to section Lists of Chapter 1, Getting Started).

for iteration in range(n): # repeat the following code n times
    ...

If the purpose of a loop is to go through a list, many languages (including Python) offer the following pattern:

for k in range(...):
    ...
    element = my_list[k]

If the purpose of that code were to go through the list my_list, the preceding code would not make it very clear. For this reason, a better way to express this is as follows...