Removing elements that have consecutive duplicates

Question

I was curios about the question: Eliminate consecutive duplicates of list elements, and how it should be implemented in Python.

What I came up with is this:

Answer 1

A "lazy" approach would be to use itertools.groupby.

import itertools

list1 = [1, 2, 3, 3, 4, 3, 5, 5]
list1 = [g for g, _ in itertools.groupby(list1)]
print(list1)

outputs

[1, 2, 3, 4, 3, 5]

Answer 2

Another possible one-liner, using functools.reduce (excluding the import) - with the downside that string and list require slightly different implementations:

>>> from functools import reduce

>>> reduce(lambda a, b: a if a[-1:] == [b] else a + [b], [1,1,2,3,4,4,5,1,2], [])
[1, 2, 3, 4, 5, 1, 2]

>>> reduce(lambda a, b: a if a[-1:] == b else a+b, 'aa  bbb cc')
'a b c'

Answer 3

If you use Python 3.8+, you can use assignment expression :=:

list1 = [1, 2, 3, 3, 4, 3, 5, 5]

prev = object()
list1 = [prev:=v for v in list1 if prev!=v]

print(list1)

Prints:

[1, 2, 3, 4, 3, 5]