Python - Use 'set' to find the different items in list

Question

I need to compare two lists in Python, and I know about using the set command to find similar items, but is there a another command I could use that would automatically compare them, instead of having to code for it?

I would like to find the items that aren't in each one. Say list one is as follows:

[1, 2, 3, 4, 5, 6]  

and list two is:

[1, 2, 3, 4, 6] 

I want to find that 5 is missing from the list, hopefully by a command, but I do know how to loop through comparing.

Answer 1

The docs are a good place to start. Here are a couple examples that might help you determine how you want to compare your sets.

To find the intersection (items that are in both sets):

>>> a = set([1, 2, 3, 4, 5, 6]) >>> b = set([4, 5, 6, 7, 8, 9]) >>> a & b set([4, 5, 6]) 

To find the difference (items that only in one set):

>>> a = set([1, 2, 3, 4, 5, 6]) >>> b = set([4, 5, 6, 7, 8, 9]) >>> a - b set([1, 2, 3]) >>> b - a set([7, 8, 9]) 

To find the symmetric difference (items that are in one or the other, but not both):

>>> a = set([1, 2, 3, 4, 5, 6]) >>> b = set([4, 5, 6, 7, 8, 9]) >>> a ^ b set([1, 2, 3, 7, 8, 9]) 

Hope that helps.

Answer 2

Looks like you need symmetric difference:

a = [1,2,3] b = [3,4,5]  print(set(a)^set(b))   >>> [1,2,4,5]