Question

If I try:

mi_list = ['three', 'small', 'words'] mi_set = set(mi_list) mi_set.remove('small') print mi_set   

I get:

set(['three', 'words'])   

which is what I expect. Whereas If I try:

mi_list = ['three', 'small', 'words'] mi_set = set(mi_list).remove('small') print mi_set 

I get:

None 

Why?

I suspect there’s a clue in that if I try to remove an element that isn’t present – eg ‘big’ – an error gets reported:

KeyError: 'big' 

Answer 1

set.remove returns nothing (None).

Your code assigns the return value of set.remove to the variable mi_set. Therefore, mi_set is None.