Iterate consecutive elements in a list in Python such that the last element combines with first

Question

I have a list:

L = [1,2,3,4,5,6,7,8]

I want to iterate consecutive elements in the list such that, when it comes to last element i'e 8 it pairs with the first element 1.

The final output I want is:

[1,2],[2,3],[3,4],[4,5],[5,6],[6,7],[7,8],[8,1]

I tried using this way:

for first,second in zip(L, L[1:]):
    print([first,second])

But I am getting only this result:

[1,2],[2,3],[3,4],[4,5],[5,6],[6,7],[7,8]

How do I make a pair of last element with first? I have heard about the negative indexing property of a list.

Answer 1

You can just append the front element(s) to the back.

for first,second in zip(L, L[1:] + L[:1]):
    print([first,second])

Answer 2

You can simply extend the second list in zip() with a list with only the first item, something like:

for first, second in zip(L, L[1:] + L[0:1]):  # or simply zip(L, L[1:] + L[:1])
    print([first, second])

Answer 3

You can use cycle to cycle the lists (in combination with islice to skip the first element):

from itertools import cycle, islice

L = [1,2,3,4,5,6,7,8]
rest_L_cycled = islice(cycle(L), 1, None)
items = zip(L, rest_L_cycled)
print(list(items))

This is easily extensible. Note that it relies on the fact that zip halts on the shorter list (the second argument is an infinite cycle). It also does everything lazily and does not create any intermediate list (well, except for the printed list) :-)