Question

This exercise is taken from Google’s Python Class:

D. Given a list of numbers, return a list where
all adjacent == elements have been reduced to a single element,
so [1, 2, 2, 3] returns [1, 2, 3]. You may create a new list or
modify the passed in list.

Here’s my solution so far:

def remove_adjacent(nums):
  if not nums:
    return nums

  list = [nums[0]]

  for num in nums[1:]:
    if num != list[-1]:
        list.append(num)

  return list

But this looks more like a C program than a Python script, and I have a feeling this can be done much more elegant.

EDIT

So [1, 2, 2, 3] should give [1, 2, 3] and [1, 2, 3, 3, 2] should give [1, 2, 3, 2]

Answer 1

There is function in itertools that works here:

import itertools
[key for key,seq in itertools.groupby([1,1,1,2,2,3,4,4])]

You can also write a generator:

def remove_adjacent(items):
    # iterate the items
    it = iter(items)
    # get the first one
    last = next(it)
    # yield it in any case
    yield last
    for current in it:
        # if the next item is different yield it
        if current != last:
            yield current
            last = current
        # else: its a duplicate, do nothing with it

print list(remove_adjacent([1,1,1,2,2,3,4,4]))