Question

How to pass all items in list, through for loop. If iteration starts not from first element.

Lets jump to example right away:

We have list ['a','b','c','d'].

I want to go through all the items in this list using for loop. But if iteration starts not from first element, I want to came back oand start from first element.
Something like this:

lst = ['a','b','c','d']

start_index = 2

for loop_num in range(len(lst)):
    item = lst[start_index+loop_num]
    print item

It will print me:

>> c,d

Than rises IndexOutOfRange error

But I want result to be like this:

>> c, d, a, b

and if we change the start_index variable to 1 result suppose to be:

b, c, d, a

in case of start_index = 0

result: a, b, c, d

Answer 1

lst = ['a','b','c','d']

start_index = 2

for loop_num in range(len(lst)):
    item = lst[(start_index+loop_num) % len(lst)]
    print item

% – it is special operation. 3 % 5 = 3, 10 % 5 = 0,
read about it Remainder and Python Doc