Author Dusty Phillips Reviewers

my_artists is to bands:
issuperset: True
issubset: False
difference: {'Sarah Brightman', 'Vixy and Tony'}
********************
bands is to my_artists:
issuperset: False
issubset: True
difference: set()
The 
difference
method, in the second case, returns an empty set, since there are
no items in 
bands
that are not in 
my_artists
.
The 
union
, 
intersection
, and 
difference
methods can all take multiple sets as 
arguments; they will return, as we might expect, the set that is created when the 
operation is called on all the parameters.
www.it-ebooks.info

---

Chapter 6
[
 177 
]
So the methods on sets clearly suggest that sets are meant to operate on other sets, 
and that they are not just containers. If we have data coming in from two different 
sources and need to quickly combine them in some way, to determine where the data 
overlaps or is different, we can use set operations to efficiently compare them. Or 
if we have data incoming that may contain duplicates of data that has already been 
processed, we can use sets to compare the two and process only the new data.
Finally, it is valuable 
to know that sets are much more efficient than lists when 
checking for membership using the 
in
keyword. If you use the syntax 
value in 
container
on a set or a list, it will return 
True
if one of the elements in 
container
is 
equal to 
value
and 
False
otherwise. However, in a list, it will look at every object in 
the container until it finds the value, whereas in a set, it simply hashes the value and 
checks for membership. This means that a set will find the value in the same amount 
of time no matter how big the container is, but a list will take longer and longer to 
search for a value as the list contains more and more values.