Changing the value of range during iteration in Python

Question

>>> k = 8
>>> for i in range(k):
        print i
        k -= 3
        print k

Above the is the code which prints numbers from <

Answer 1

The expression range(k) is evaluated just once, not on every iteration. You can't set k and expect the range(k) result to change, no. From the for statement documentation:

The expression list is evaluated once; it should yield an iterable object.

You can use a while loop instead:

i = 0
k = 8
while i < k:
    print i
    i += 1
    k -= 3

A while loop does re-evaluate the test each iteration. Referencing the while statement documentation:

This repeatedly tests the expression and, if it is true, executes the first suite