Python-5(Sets)

1.Python Sets :

1.1 introduction :

• A set is an unordered collection data type with no duplicate elements. Sets are iterable and mutable. The elements appear in an arbitrary order when sets are iterated.
• Sets are commonly used for membership testing, removing duplicates entries, and also for operations such as intersection, union, and set difference.
• A set is a collection which is unordered and unindexed. In Python sets are written with curly brackets.

Example :

1. Creating a set

   thisset = {"apple", "banana", "cherry"}      
   print(thisset)
   
   #output
   {'banana', 'cherry', 'apple'}

1.2 Access Items :

• You cannot access items in a set by referring to an index, since sets are unordered the items has no index.
• But you can loop through the set items using a for loop, or ask if a specified value is present in a set, by using the in keyword. 

Example :

1. Loop through the set, and print the values

   thisset = {"apple", "banana", "cherry"}
   
   for x in thisset:
     print(x)
   
   #output
   cherry
   banana
   apple 

1.3 Adding the item :

• Python set add(element) This will add element to a set:
•  To add more than one item to a set use the update() method.

Example:

1. Add an item to a set, using the add() method

   thisset = {"apple", "banana", "cherry"}
   
   thisset.add("orange")
   
   print(thisset)
   
   #output
   {'banana', 'cherry', 'apple', 'orange'}

    

2. you can pass a list to the update method and this will update the setA with the elements.

    # pass a list with elements 11 and 12 
    setA.update([11, 12])
    # check if setA is updated with the elements.
    print(setA)
   
   #output
       {1, 2, 3, 4, 5, 6, 7, 8, 11, 12, (9, 10)}

    

1.4 Removing item :

• Python set discard(element) and remove(element) Used to remove element from the set 

Example :

1. Remove "banana" by using the remove() method:

   thisset = {"apple", "banana", "cherry"}
   
   thisset.remove("banana")
   
   print(thisset)
   
   #output
   {'cherry', 'apple'}

    

 1.5  set() Constructor :

Example :​

thisset = set(("apple", "banana", "cherry"))
print(thisset)

#output
{'cherry', 'banana', 'apple'}