The set data type represents a collection of unordered, unique elements.

Sets are mutable meaning that they can be modified by adding, removing, or replacing elements.

The add() method is used  to add a single element to a set. 

myset.add(e)
e The element to be added to the set.

The add() methods adds element e to the set. There will be no effect if the element is already present.

myset = {'Python', 'Java', 'C++'}

#add elements to the set
myset.add('PHP')
myset.add('HTML')
myset.add('Javascript')

print(myset)

add() vs update()

If we want to add multiple elements to a set, we may use the add() method with a for loop as follows.

myset = {'Python', 'Java', 'C++'}

elements = ['PHP', 'HTML', 'Javascript']

#add the elements to the set
for e in elements:
    myset.add(e)

print(myset)

However, the set class also contains the update()  methods which   allows you to add multiple elements to a set simultaneously. This approach is more convenient than adding each element individually via a loop.

myset = {'Python', 'Java', 'C++'}

elements = ['PHP', 'HTML', 'Javascript']

#use update() to add elements to the set
myset.update(elements)

print(myset)