I am looking to remove the contents of one array from another.
array_2 = ['one' , "two" , "one", "three", "four"]
array_1 = ['one', "two"]
My first thought was to use list comprehensions
array_3 = [x for x in array_2 if x not in array_1]
However this will remove the duplicate item
result : ['three', 'four']
I want to only remove "one" once from the array as I am looking for a list subtraction. So I want the result to be : ['one', 'three', 'four'].
What is a good pythonic way to achieve this ?
I am just going to collect the excellent solutions already given above.
If you care about maintaining the original order in which the elements in array_2 were, then I think you have to use remove:
array_1 = ['one', 'two']
array_2 = ['one', 'two', 'one', 'three', 'four']
array_3 = list(array_2)
for x in array_1:
try:
array_3.remove(x)
except ValueError:
pass
print(array_3)
If it does not matter what the final order of elements is, then using Counter is much more efficient as it only loops over both lists once:
from collections import Counter
array_1 = ['one', 'two']
array_2 = ['one', 'two', 'one', 'three', 'four']
array_3 = list((Counter(array_2) - Counter(array_1)).elements())
print(array_3)