Get difference between two lists with Unique Entries

Question

I have two lists in Python:

temp1 = ['One', 'Two', 'Three', 'Four']
temp2 = ['One', 'Two']

Assuming the elements in each list are unique, I want to create a third list with items from the first list which are not in the second list:

temp3 = ['Three', 'Four']

Are there any fast ways without cycles and checking?

Answer 1

To get elements which are in temp1 but not in temp2 (assuming uniqueness of the elements in each list):

In [5]: list(set(temp1) - set(temp2))
Out[5]: ['Four', 'Three']

Beware that it is asymmetric :

In [5]: set([1, 2]) - set([2, 3])
Out[5]: set([1]) 

where you might expect/want it to equal set([1, 3]). If you do want set([1, 3]) as your answer, you can use set([1, 2]).symmetric_difference(set([2, 3])).