sets in python

Set example
To create a set, we use the set() function.

#!/usr/bin/env python   x = set(["Postcard", "Radio", "Telegram"]) print(x)

If we add the same item element multiple times, they are removed.  A set may not contain the same element multiple times.


#!/usr/bin/env python

x = set(["Postcard", "Radio", "Telegram", "Postcard"])
print(x)

Simple notation

If you use Python version 2.6 or a later version, you can use a simplified notation:

#!/usr/bin/env python   x = set(["Postcard", "Radio", "Telegram"]) print(x)   y = {"Postcard","Radio","Telegram"} print(y)

Set Methods

Clear elements from set
To remove all elements from sets:

#!/usr/bin/env python
 
x = set(["Postcard", "Radio", "Telegram"])
x.clear()
print(x)

Add elements to a set

To add elements to a set:

#!/usr/bin/env python   x = set(["Postcard", "Radio", "Telegram"]) x.add("Telephone") print(x)

Remove elements to a set

To remove elements to a set:

!/usr/bin/env python
 
x = set(["Postcard", "Radio", "Telegram"])
x.remove("Radio")
print(x)

Difference between two sets
To find the difference between two sets use:

#!/usr/bin/env python x = set(["Postcard", "Radio", "Telegram"]) y = set(["Radio","Television"]) print( x.difference(y) ) print( y.difference(x) )

Be aware that x.difference(y) is different from y.difference(x).

Subset
To test if a set is a subset use:

#!/usr/bin/env python   x = set(["a","b","c","d"]) y = set(["c","d"]) print( x.issubset(y) )<b> </b>

Super-set
To test if a set is a super-set:

#!/usr/bin/env python   x = set(["a","b","c","d"]) y = set(["c","d"]) print( x.issuperset(y) ) Intersection To test for intersection, use: #!/usr/bin/env python   x = set(["a","b","c","d"]) y = set(["c","d"]) print( x.intersection(y) )