Python update() function in set adds elements from a set (passed as an argument) to the set.

Syntax : set1.update(set2)

Here set1 is the set in which set2 will be added.

Parameters : Update() method takes only a single argument. The single argument can be a set, list, tuples or a dictionary. It automatically converts into a set and adds to the set. 

Return value : This method adds set2 to set1 and returns nothing. 

Example of Python set update()

Example 1: Working with Python set update list

# Python program to demonstrate the
# use of update() method

list1 = [1, 2, 3]
list2 = [5, 6, 7]
list3 = [10, 11, 12]

# Lists converted to sets
set1 = set(list2)
set2 = set(list1)

# Update method
set1.update(set2)

# Print the updated set
print(set1)

# List is passed as an parameter which
# gets automatically converted to a set
set1.update(list3)
print(set1)

输出：

{1, 2, 3, 5, 6, 7}
{1, 2, 3, 5, 6, 7, 10, 11, 12}

Example 2: Python set update element in set

# Python program to demonstrate the
# use of update() method

list1 = [1, 2, 3, 4]
list2 = [1, 4, 2, 3, 5]
alphabet_set = {'a', 'b', 'c'}

# lists converted to sets
set1 = set(list2)
set2 = set(list1)

# Update method
set1.update(set2)

# Print the updated set
print(set1)

set1.update(alphabet_set)
print(set1)

输出：

{1, 2, 3, 4, 5}
{1, 2, 3, 4, 5, 'c', 'b', 'a'}

Example 3: Add elements of the dictionary to Set

number = {1, 2, 3, 4, 5}

num_Dict = {6: 'Six', 7: 'Seven', 8: 'Eight',
			9: 'Nine', 10: 'Ten'}

number.update(num_Dict)

print("Updated set: ", number)

输出：

Updated set:  {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

转载：https://www.geeksforgeeks.org/python-set-update/