从列表中删除重复项，但返回相同列表

Question

I need to remove the duplicates from a list but return the same list. So options like:

return list(set(list))

will not work for me, as it creates a new list instead.

def remove_extras(lst):
  for i in lst:
    if lst.count(i)>1:
        lst.remove(i)
  return lst

Here is my code, it works for some cases, but I dont get why it does not work for remove_extras([1,1,1,1]), as it returns [1,1] when the count for 1 should be >1.

Answer 1

You can use slice assignment to replace the contents of the list after you have created a new list. In case order of the result doesn't matter you can use set :

def remove_duplicates(l):
    l[:] = set(l)

l = [1, 2, 1, 3, 2, 1]
remove_duplicates(l)
print(l)

Output:

[1, 2, 3]

Answer 2

You can achieve this using OrderedDict which removes the duplicates while maintaining order of the list.

>>> from collections import OrderedDict
>>> itemList = [1, 2, 0, 1, 3, 2]
>>> itemList[:]=OrderedDict.fromkeys(itemList)
>>> itemList
[1, 2, 0, 3]

This has a Runtime : O(N)