Python list subtraction operation

Issue

I want to do something similar to this:

>>> x = [1,2,3,4,5,6,7,8,9,0]  
>>> x  
[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]  
>>> y = [1,3,5,7,9]  
>>> y  
[1, 3, 5, 7, 9]  
>>> y - x   # (should return [2,4,6,8,0])

But this is not supported by python lists
What is the best way of doing it?

Solution

Use a list comprehension:

[item for item in x if item not in y]

If you want to use the - infix syntax, you can just do:

class MyList(list):
    def __init__(self, *args):
        super(MyList, self).__init__(args)

    def __sub__(self, other):
        return self.__class__(*[item for item in self if item not in other])

you can then use it like:

x = MyList(1, 2, 3, 4)
y = MyList(2, 5, 2)
z = x - y   

But if you don’t absolutely need list properties (for example, ordering), just use sets as the other answers recommend.

Answered By – aaronasterling

This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0

Leave a Reply

(*) Required, Your email will not be published