Python Set difference_update()

The difference_update() updates the set calling difference_update() method with the difference of sets.

If A and B are two sets. The set difference of A and B is a set of elements that exists only in set A but not in B.

To learn more, visit Python set difference.

The syntax of difference_update() is:

A.difference_update(B)

Here, A and B are two sets. difference_update() updates set A with the set difference of A-B.

1. Return Value from difference_update()

difference_update() returns None indicating the object (set) is mutated.

Suppose,

result = A.difference_update(B)

When you run the code,

• result will be None
• A will be equal to A-B
• B will be unchanged

2. Example: How difference_update() works?

A = {'a', 'c', 'g', 'd'}
B = {'c', 'f', 'g'}

result = A.difference_update(B)

print('A = ', A)
print('B = ', B)
print('result = ', result)

Output

A =  {'d', 'a'}
B =  {'c', 'g', 'f'}
result =  None