python lists, delete content of list1 in list2

Question

I have two lists

list1=['value1', 'value2', 'value3']
list2=['value1', 'value2', 'value3', 'value4', 'value5']

I want to delete the contents of list1 from list2

Result should be :

['value4', 'value5']

Do you want to remove those elements from the existing list, or create a new, filtered list? — tobias_k, Jun 25 '20 at 09:46
https://stackoverflow.com/questions/3462143/get-difference-between-two-lists — Shijith, Jun 25 '20 at 09:51

score 3 · Accepted Answer · answered Jun 25 '20 at 09:53

You can do it by converting the list1 to set and then by list comprehension create a new list with the items from list2 that not in list1

list1=['value1', 'value2', 'value3']
list2=['value1', 'value2', 'value3', 'value4', 'value5']
list1_set = set(list1)
result = [i for i in list2 if i not in list1_set]
print(result)

Output

['value4', 'value5']

The conversion of list1 to set is from better performances since checking if an item is in a set is faster than in a list.

score 2 · Answer 2 · answered Jun 25 '20 at 09:48

2

list2 = [elem for elem in list2 if elem not in list1]

answered Jun 25 '20 at 09:48

Bram Dekker

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Technically, this does not _remove_ from `list2` but overwrite the variable with a new list. You could e.g. use `list[:] = ...` to replace all elements in `list2`. Also, converting `list1` to `set` might be faster. – tobias_k Jun 25 '20 at 09:49

score 1 · Answer 3 · answered Jun 25 '20 at 09:53

1

To print the values of items in list2 that are not in list1, you can use this code:

list1=['value1', 'value2', 'value3']
list2=['value1', 'value2', 'value3', 'value4', 'value5']

print([list2 for list2 in list2 if list2 not in list1])

answered Jun 25 '20 at 09:53

Gavin Wong

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Note, this works, but is inefficient. – juanpa.arrivillaga Jun 25 '20 at 09:55

SABRIO · Answer 4 · 2020-06-25T10:17:42.483

1

list1=['value1', 'value2', 'value3']
list2=['value1', 'value2', 'value3', 'value4', 'value5']

set_list_1 = set(list1)
set_list_2 = set(list2)
print(list(set_list_2.difference(set_list_1)))
['value4', 'value5']

edited Jun 25 '20 at 10:17

answered Jun 25 '20 at 10:01

SABRIO

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python lists, delete content of list1 in list2

4 Answers4