unique_in_order.py

"""
Implement the function unique_in_order which takes as argument a sequence and returns a list of items without any
elements with the same value next to each other and preserving the original order of elements.

For example:

unique_in_order('AAAABBBCCDAABBB') == ['A', 'B', 'C', 'D', 'A', 'B']
unique_in_order('ABBCcAD')         == ['A', 'B', 'C', 'c', 'A', 'D']
unique_in_order([1,2,2,3,3])       == [1,2,3]
"""


def unique_in_order(iterable):
    if len(iterable) == 0:
        return []
    result = [iterable[0]]
    for item in iterable:
        if item != result[-1]:
            result.append(item)
    return result