sets and subsets

[Lee Harr]

On 2004-02-11, Bart Nessux <bart_nessux at hotmail.com> wrote:
> By using lists, I can create sets of number. Suppose I have three lists. 
> One list is the super-set, one is a set that contains all the numbers 
> (just like the super-set) and the last is sub-set of the super-set. For 
> example:
>
> a = [1,2,3,4,5]	# The super-set.
> b = [1,2,3,4,5] # Looks just like the super-set, but it's not.
> c = [2,4]	# A sub-set
>
> I'd like to remove 2 & 4 from set b BECAUSE they are present in set c... 
> this would make the sets look like this:
>
> a = [1,2,3,4,5]
> b = [1,3,5]
> c = [2,4]
>
> How do I test set c to find what it contains and then look at set b to 
> see if it contains any of those same numbers, and if so, remove them.
>


>>> from sets import Set
>>> a = Set([1, 2, 3, 4, 5])
>>> b = Set([1, 2, 3, 4, 5])
>>> c = Set([2, 4])
>>> s = b - c
>>> s
Set([1, 3, 5])