Add an item between each item already in the list [duplicate]

Answer 1

Adapting this answer to a similar question:

>>> input = ['a', 'b', 'c', 'd', 'e']
>>> sep = ['-'] * len(input)
>>> list(sum(zip(input, sep), ())[:-1])
['a', '-', 'b', '-', 'c', '-', 'd', '-', 'e']

Another answer to the same question does this using itertools and a slightly modified separator list:

>>> import itertools
>>> sep = ['-'] * (len(input) - 1)
>>> list(it.next() for it in itertools.cycle((iter(input), iter(sep))))
['a', '-', 'b', '-', 'c', '-', 'd', '-', 'e']

Answer 2

>>> list('-'.join(ls))
['a', '-', 'b', '-', 'c', '-', 'd', '-', 'e']
>>>