How do you check if anything is new in a list? (python)

Question

I would like to know how to check if anything is new in a list, like this:

list_1 = [10, 30, 25]
list_2 = get_updated_list()
new_items = get_new_items(list_2)
if new_items is not []:
    print('Something is new')

I would highly appreciate it if someone had a solution, I've been thinking on how to do this for so long.

Does this answer your question? [Get difference between two lists](https://stackoverflow.com/questions/3462143/get-difference-between-two-lists) — รยקคгรђשค, Oct 17 '20 at 11:46

score 2 · Answer 1 · answered Oct 17 '20 at 11:45

2

You could use the built-in set difference.

s1 = set(list_1)
s2 = set(list_2)

diff = s1.difference(s2)
if diff:
    print("Something is new")

answered Oct 17 '20 at 11:45

Christopher Peisert

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score 0 · Accepted Answer · answered Oct 17 '20 at 11:47

If you just care about the sets of values in list_1 and list_2, without regard to their order or the number of times they occur, then you can use a simple set difference:

>>> list_1 = [10, 30, 25]
>>> list_2 = [10, 25, 45]
>>> list(set(list_2) - set(list_1))
[45]
>>>

This example shows the values that are present in list_2 but not in list_1. To see values that were removed, you can reverse the subtraction.

score 0 · Answer 3 · answered Oct 17 '20 at 11:47

0

An easy way, just do - and convert back to list:

list(set(list2)-set(list1))

answered Oct 17 '20 at 11:47

Wasif

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But what if list_1 for instance is [0, 2, 2, 5]? – Yuval.R Oct 17 '20 at 11:48

How do you check if anything is new in a list? (python)

3 Answers3