python - Duplicate elements in a list

Question

I have a list in Python:

l = ['a', 'c', 'e', 'b']

I want to duplicate each element immediately next to the original.

ll = ['a', 'a', 'c', 'c', 'e', 'e', 'b', 'b']

The order of the elements should be preserved.

Answer 1

>>> l = ['a', 'c', 'e', 'b']
>>> [x for pair in zip(l,l) for x in pair]
['a', 'a', 'c', 'c', 'e', 'e', 'b', 'b']

Or

>>> from itertools import repeat
>>> [x for item in l for x in repeat(item, 2)]
['a', 'a', 'c', 'c', 'e', 'e', 'b', 'b']