Python difference_update() method helps differentiate the set in the in-place. For example, the previously discussed Python set difference() helps determine the difference between two sets. It returns the new set with a different value, but the difference_update() updates the existing caller set.

For example, if **A = {a,b,c,d,e,f} **and **B={a,e,f,g} **are two sets and if we want to find A-B then the result will be **{b,c,d}, **also this method will modify the set A with values **{b,c,d}.**

Similarly, if we want to find **B-A, **the result will be **{f,g}, **and this method will modify the set B with this value but set A will remain unchanged.

**Python Set difference_update**

**Python Set difference_update()** is a built-in method that finds the difference between two sets; also, it modifies the caller set with the result set. In the set difference method, we see the difference between the two sets and return the difference as a new set.

**Syntax**

First_Set.difference_update(Second_Set)

The above syntax will help us to find the difference between *First_Set-Second_Set.*

So, If we want to find **A-B, **the syntax will be:

A.difference_update(B)

**Return Value**

The function does not return any value, and it returns None. But it changes the value of the caller set.

See the following code example.

# app.py # Declaring two sets A = {'a', 'b', 'c', 'd', 'e'} B = {'a', 'e', 'f', 'g'} # Now we will apply difference_update() to find A-B result = A.difference_update(B) # Now we will check the value of A, B, and result print("Value of A is: ", A) print("Value of B is: ", B) print("Value of result is: ", result)

**Output**

Value of A is: {'c', 'b', 'd'} Value of B is: {'f', 'e', 'a', 'g'} Value of result is: None

From the above example, we can see that we could find the difference between sets** A** and **B,** but the method modified the value of set **A **with the value of **A-B**.

Also, **B **remains unchanged, and the value of the **result** is **None, **as the function does not return anything.