lst = [1, 2, 3, 4, 5, 6]
for i, item in enumerate(lst):
    while i < 3:
        print (i, item)
        i += 1
print ('---')
for i in range(len(lst)):
    while i < 3:
        print (i, lst[i])
        i += 1
print ('---')
i = 0
while i < len(lst):
    while i < 3:
        print (i, lst[i])
        i += 1
    i += 1