Author Dusty Phillips Reviewers

All: {'Sarah Brightman', "Guns N' Roses", 'Vixy and Tony',
'Savage Garden', 'Opeth', 'Nickelback'}
Both: {"Guns N' Roses"}
Either but not both: {'Savage Garden', 'Opeth', 'Nickelback',
'Sarah Brightman', 'Vixy and Tony'}
These methods all return the same result, regardless of which set calls the other.
We can say 
my_artists.union(auburns_artists)
or 
auburns_artists.
union(my_artists)
and get the same result. There are also methods that return 
different results depending on who is the caller and who is the argument.
These methods include 
issubset
and 
issuperset
, which are the inverse of each 
other. Both return a 
bool
. The 
issubset
method returns 
True
, if all of the items in 
the calling set are also in the set passed as an argument. The 
issuperset
method 
returns 
True
if all of the items in the argument are also in the calling set. Thus 
s.issubset(t)
and 
t.issuperset(s)
are identical. They will both return 
True
if 
t
contains all the elements in 
s
.
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Python Data Structures
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 176 
]
Finally, the 
difference
method returns all the elements that are in the calling set, 
but not in the set passed as an argument; this is like half a 
symmetric_difference
. 
The 
difference
method can also be represented by the 
-
operator. The following 
code illustrates these methods in action:
my_artists = {"Sarah Brightman", "Guns N' Roses",
"Opeth", "Vixy and Tony"}
bands = {"Guns N' Roses", "Opeth"}
print("my_artists is to bands:")
print("issuperset: {}".format(my_artists.issuperset(bands)))
print("issubset: {}".format(my_artists.issubset(bands)))
print("difference: {}".format(my_artists.difference(bands)))
print("*"*20)
print("bands is to my_artists:")
print("issuperset: {}".format(bands.issuperset(my_artists)))
print("issubset: {}".format(bands.issubset(my_artists)))
print("difference: {}".format(bands.difference(my_artists)))
This code simply prints out the response of each method when called from one set
on the other. Running it gives us the following output: