**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. 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()**

Python Set issubset() is a built-in 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. This means the second set must contain values that are present in the first set.

**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

**Example**

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 a multiple of 4 from 4 to 10, and Set3, which includes a 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

That’s it for this tutorial.

**See also**

Python set intersection_update()