Python Set update() Function
The Set update() method adds elements from another set (or any other iterable) to the current set, without duplicates.
If you do not want to update the original set, use union() method.
Syntax
my_set.update(set1, set2, ...)
update() Parameters
Python Set update() function parameters:
| Parameter | Condition | Description |
|---|---|---|
set1, set2, ... | Optional | A comma-separated list of one or more sets to merge with |
If no arguments are provided, the method does not perform any operation, leaving the original set unaltered.
You can also pass iterables like list, tuple, dictionary or string. In that case, update() method first converts the iterables into sets and then adds elements to the first set.
update() Return Value
Python Set update() function does not return any values: it modifies the set in place by adding elements from another set (or any other iterable), without duplicates.
Examples
Example 1: Update of Two Sets with update() method
A = {'Tom', 'Anna'}
B = {'David', 'Ryan'}
A.update(B)
print(A) # Output: {'David', 'Ryan', 'Anna', 'Tom'}
output
{'David', 'Ryan', 'Anna', 'Tom'}
Example 2: Update between Multiple Sets
The update() method allows to adding elements from multiple sets, without duplicates:
A = {1, 2, 3}
B = {3, 4, 5, 6, 7}
C = {6, 7, 8, 9, 10}
A.update(B, C)
print(A) # Output: {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
output
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
Example 3: Update between a Set and a List
You can also pass iterables like list: update() first converts the iterables to sets and then adds elements.
For example:
# create a Set A
A = {'a', 'e', 'i', 'o', 'u'}
# create a List B
B = ['d', 'e', 'f']
A.update(B)
print(A) # Output: {'a', 'i', 'u', 'f', 'e', 'd', 'o'}
output
{'a', 'i', 'u', 'f', 'e', 'd', 'o'}
Example 4: Update between a Set and a Tuple
You can also pass iterables like tuple: update() first converts the iterables to sets and then adds elements.
For example:
# create a Set A
A = {'a', 'e', 'i', 'o', 'u'}
# create a Tuple B
B = ('d', 'e', 'f')
A.update(B)
print(A) # Output: {'a', 'i', 'u', 'f', 'e', 'd', 'o'}
output
{'a', 'i', 'u', 'f', 'e', 'd', 'o'}
Example 5: Update between a Set and a Dictionary
You can also pass iterables like dictionary: update() first converts the iterables to sets and then adds elements.
The dictionary keys are used for update(), not the values!
For example:
# create a Set A1 and A2
A1 = {'a', 'e', 'i', 'o', 'u'}
A2 = {'a', 'e', 'i', 'o', 'u'}
# create Dictionary B and C
B = {1: 'd', 2: 'e', 3: 'f'}
C = {'d': 1, 'e': 2, 'f': 3}
A1.update(B)
A2.update(C)
print(A1) # Output: {1, 2, 3, 'a', 'e', 'o', 'i', 'u'}
print(A2) # Output: {'a', 'e', 'f', 'o', 'd', 'i', 'u'}
output
{1, 2, 3, 'a', 'e', 'o', 'i', 'u'}
{'a', 'e', 'f', 'o', 'd', 'i', 'u'}
Example 6: Update between a Set and a String
You can also pass iterables like string: update() first converts the iterables to sets and then adds elements.
For example:
# create a Set A
A = {'a', 'e', 'i', 'o', 'u'}
# create a String B
B = 'def'
A.update(B)
print(A) # Output: {'a', 'i', 'u', 'o', 'e'}
output
{'a', 'i', 'u', 'o', 'e'}
Equivalent Operator |= for update()
Set Update can be performed with the |= operator as well, providing an alternative to the update() method.
A = {1, 2, 3, 4, 5}
B = {3, 4, 5, 6, 7}
# equivalent to: A.update(B)
A |= B
print(A) # Output: {1, 2, 3, 4, 5, 6, 7}
output
{1, 2, 3, 4, 5, 6, 7}
Moreover, you can use the |= operator with multiple sets:
A = {1, 2, 3}
B = {3, 4, 5, 6, 7}
C = {6, 7, 8, 9, 10}
# equivalent to result = A.update(B, C)
A |= B | C
print(A) # Output: {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
output
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}