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# Python Set issubset() Method Example

Python Set issubset() is an inbuilt function that is used to find whether a set is a subset of another set or not. If all the elements of one set are present in another set, then the first set is called a subset of the second set. Means, the second set must contain values that are present in the first set.

Lets, assume A={1,2,4} and B={1,2,3,4,5} are two sets. So we can see the following figure.

## Python Set issubset() Method

Python set issubset() method returns True if all items of a set are present in another set (passed as an argument). If not, then it returns False. The set A is said to be the subset of set B if all items of A are in B. Here, set A is a subset of B.

#### Syntax

`First_Set.issubset(Second_Set)`

Here, this syntax will check if First_Set is a subset of Second_Set or not.

#### Return Value

The function returns two types of values-

True: If First_Set is a subset of Second_Set

False: If First_Set is not a subset of Second_Set

See the following code.

```# app.py

# Declaring two sets
# Even nums between 2 and 10
set1 = {2, 4, 6, 8, 10}
# Multiple of 4 from 4 to 10
set2 = {4, 8}
# Multiple of 4 from 4 to 20
set3 = {4, 8, 12, 16, 20}

# priting both the sets
print("Set1 is: ", set1)
print("Set2 is : ", set2)
print("Set3 is: ", set3)
# Now we will find if they are disjoint
print("Is Set2 Subset of Set1? ", set2.issubset(set1))
print("Is Set3 Subset of Set1? ", set3.issubset(set1))
```

#### Output

```Set1 is:  {2, 4, 6, 8, 10}
Set2 is :  {8, 4}
Set3 is:  {4, 8, 12, 16, 20}
Is Set2 Subset of Set1?  True
Is Set3 Subset of Set1?  False```

In this program, we have declared three sets, Set1, which is even numbers from 1 to 10, Set2, which contains multiple of 4 from 4 to 10 and Set3, which includes multiple of 4 from 4 to 20.

Now, we are finding if Set2 is a subset of Set1 or not. So, we can see that all the elements of Set2 are present in Set1. So, Set2 is a subset of Set1.

On the other hand, we can see that not all the elements are present in Set1 of Set3, so it is not a subset of Set1. That’s why the return value is False.

See the following second example.

```# app.py

A = {11, 21, 19}
B = {11, 21, 19, 46, 18}
C = {11, 21, 46, 18}

# Returns True
print(A.issubset(B))

# Returns False
# B is not subset of A
print(B.issubset(A))

# Returns False
print(A.issubset(C))

# Returns True
print(C.issubset(B))
```

#### Output

```python3 app.py
True
False
False
True```

Finally,

Python set isdisjoint()

Python set intersection_update()

Python set intersection()