set datatype in python language || which operation can perform on set || Python lec 8

Published: 21 September 2020
on channel: The Art of Computing

Python Set
A Python set is the collection of the unordered items. Each element in the set must be unique, immutable, and the sets remove the duplicate elements. Sets are mutable which means we can modify it after its creation.

Unlike other collections in Python, there is no index attached to the elements of the set, i.e., we cannot directly access any element of the set by the index. However, we can print them all together, or we can get the list of elements by looping through the set.

Creating a set
The set can be created by enclosing the comma-separated immutable items with the curly braces {}. Python also provides the set() method, which can be used to create the set by the passed sequence.

Adding items to the set
Python provides the add() method and update() method which can be used to add some particular item to the set. The add() method is used to add a single element whereas the update() method is used to add multiple elements to the set.

Removing items from the set
Python provides the discard() method and remove() method which can be used to remove the items from the set. The difference between these function, using discard() function if the item does not exist in the set then the set remain unchanged whereas remove() method will through an error.

We can also use the pop() method to remove the item. Generally, the pop() method will always remove the last item but the set is unordered, we can't determine which element will be popped from set.

Difference between discard() and remove()
Despite the fact that discard() and remove() method both perform the same task, There is one main difference between discard() and remove().

If the key to be deleted from the set using discard() doesn't exist in the set, the Python will not give the error. The program maintains its control flow.

On the other hand, if the item to be deleted from the set using remove() doesn't exist in the set, the Python will raise an error.

Python Set Operations
Set can be performed mathematical operation such as union, intersection, difference, and symmetric difference. Python provides the facility to carry out these operations with operators or methods. We describe these operations as follows.

Union of two Sets
The union of two sets is calculated by using the pipe (|) operator. The union of the two sets contains all the items that are present in both the sets.

Intersection of two sets
The intersection of two sets can be performed by the and & operator or the intersection() function. The intersection of the two sets is given as the set of the elements that common in both sets.

The intersection_update() method
The intersection_update() method removes the items from the original set that are not present in both the sets (all the sets if more than one are specified).

The intersection_update() method is different from the intersection() method since it modifies the original set by removing the unwanted items, on the other hand, the intersection() method returns a new set.

Difference between the two sets
The difference of two sets can be calculated by using the subtraction (-) operator or intersection() method. Suppose there are two sets A and B, and the difference is A-B that denotes the resulting set will be obtained that element of A, which is not present in the set B.

Symmetric Difference of two sets
The symmetric difference of two sets is calculated by ^ operator or symmetric_difference() method. Symmetric difference of sets, it removes that element which is present in both sets.

Set comparisons
Python allows us to use the comparison operators with the sets by using which we can check whether a set is a subset, superset, or equivalent to other set. The boolean true or false is returned depending upon the items present inside the sets.

Python program to find common elements in three lists using sets

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