Python set Method - intersection_update()

The intersection_update() method in Python is used to update a set with the intersection of itself and one or more other sets. The method modifies the original set in place, and returns None.

The syntax for the intersection_update() method is as follows:

set1.intersection_update(set2, set3, ...)

Here, set1 is the set that needs to be updated, and set2, set3, etc. are the sets that are used to compute the intersection. The method modifies set1 in place to contain only the elements that are common to itself and all the other sets.

Example:

# Creating three sets
set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}
set3 = {4, 5, 6, 7}

# Updating set1 with the intersection of itself and the other sets
set1.intersection_update(set2, set3)

# Displaying the sets after intersection update
print(set1)   # Output: {4}
print(set2)   # Output: {3, 4, 5, 6}
print(set3)   # Output: {4, 5, 6, 7}

In the above example, the intersection_update() method is used to update set1 with the intersection of itself, set2, and set3. Since the intersection of these sets is {4}, set1 is modified to contain only the element 4. The original sets and the updated set1 are printed to show their contents.

If any of the sets used to compute the intersection is empty, the intersection will also be empty:

# Creating an empty set and two non-empty sets
empty_set = set()
set1 = {1, 2, 3}
set2 = {3, 4, 5}

# Updating empty_set with the intersection of the sets
empty_set.intersection_update(set1, set2)

# Displaying the sets after intersection update
print(empty_set)   # Output: set()
print(set1)        # Output: {1, 2, 3}
print(set2)        # Output: {3, 4, 5}

In this case, since empty_set is empty, the intersection of the sets set1 and set2 is also empty. Therefore, empty_set remains empty after the intersection update.