Python Set issubset() Method

The Set issubset() method returns True if all items in the set are present in the specified set. Otherwise, it returns False.

Syntax

my_set.issubset(other_set)

issubset() Parameters

Python Set issubset() method parameters:

issubset() Return Value

Python Set issubset() method returns

• True if set my_set is a subset of other_set
• False if set my_set is not a subset of other_set

Examples

Example 1: Check if a Set is Subset of Another Set

If set A is subset of B, then issubset() returns True:

A = {'Anna', 'David'}
B = {'Tom', 'David', 'Anna'}

print(A.issubset(B)) # Output: True

output

True

If set A is not subset of B, then issubset() returns False:

A = {'Tom', 'David', 'Anna'}
B = {'Anna', 'David'}

print(A.issubset(B)) # Output: False

output

False

Example 2: Check if a Set is Subset of a List

You can also pass iterables like list: issubset() method first converts the iterables into sets and then verifies if the first set is a subset of the second one.

For example:

A = {'a', 'e'}

B = ['a', 'e', 'i', 'o', 'u']
C = ['e', 'i', 'o', 'u']

print('A is subset of B:', A.issubset(B)) # Output: A is subset of B: True
print('A is subset of C:', A.issubset(C)) # Output: A is subset of C: False

output

A is subset of B: True
A is subset of C: False

Example 3: Check if a Set is Subset of a Tuple

You can also pass iterables like tuple: issubset() method first converts the iterables into sets and then verifies if the first set is a subset of the second one.

For example:

A = {'a', 'e'}

B = ('a', 'e', 'i', 'o', 'u')
C = ('e', 'i', 'o', 'u')

print('A is subset of B:', A.issubset(B)) # Output: A is subset of B: True
print('A is subset of C:', A.issubset(C)) # Output: A is subset of C: False

output

A is subset of B: True
A is subset of C: False

Example 4: Check if a Set is Subset of a Dictionary

You can also pass iterables like dictionary: issubset() method first converts the iterables into sets and then verifies if the first set is a subset of the second one.

For example:

A = {'a', 'e'}

B = {1: 'a', 2: 'e', 'f': 3}
C = {'a': 1, 'e': 2, 'f': 3}

print('A is subset of B:', A.issubset(B)) # Output: A is subset of B: False
print('A is subset of C:', A.issubset(C)) # Output: A is subset of C: True

output

A is subset of B: False
A is subset of C: True

Example 5: Check if a Set is Subset of a String

You can also pass iterables like string: issubset() method first converts the iterables into sets and then verifies if the first set is a subset of the second one.

For example:

A = {'a', 'e'}

B = 'aeiou'
C = 'aiou'

print('A is subset of B:', A.issubset(B)) # Output: A is subset of B: True
print('A is subset of C:', A.issubset(C)) # Output: A is subset of C: False

output

A is subset of B: True
A is subset of C: False

Example 6: Check if a Set is Subset of Itself

A = {'a', 'e'}

print('A is subset of A:', A.issubset(A)) # Output: A is subset of A: True

output

A is subset of A: True

Equivalent Operator <= for issubset()

Check if a set is a subset of another set can be performed with the <= operator as well, providing an alternative to the issubset() method.

A = {1, 2, 3}
B = {1, 2, 3, 4, 5}

print(A.issubset(B)) # Output: True
print(B.issubset(A)) # Output: False

print(A <= B) # Output: True
print(B <= A) # Output: False

output

True
False
True
False

Find Proper Subset with < operator

To test if the set is a proper subset of other, you can use < comparison operator.

For example:

A = {1, 2, 3}
B = {1, 2, 3, 4, 5}
C = {1, 2, 3, 4, 5}

print(A < B) # Output: True
print(B < C) # Output: False

output

True
False