The set add() function of python is used to add a specified element into a set.

As we know, sets in mathematics do not allow repetition. Similarly, if you want to add an element already existing in a set, it will not add that.

## Python set add() function syntax :

``setvariable.add(element)``

### Example 1 :

``s = {2,3,4,5}s.add('a')print(s)``

### Output :

``{2, 3, 4, 5, 'a'}``

### Example 2:

``````s = {2,3,4,5}
print(s)``````

### Output :

``{2, 3, 4, 5}``

As you can see, 2 is not added because it is already there.

### Example 3:

``````s = {2,3,4,5}

### Output :

``None``

“None “ is because the return value of add method is none. And here, we print the s.add() method not “s”. That’s why we got None.

### Example 4:

``````s = {2,3,4,5}
print(s)``````

### Output :

``{2, 3, 4, 5, '2'}``

In the above example, we add a “2” as a string(because it is in double quotes)in a set. Therefore, both 2 can add in the set. But the types of both the 2 are different.

## How to use python set add function with a Tuple :

Adding a tuple in a set we have two methods: add() method, update() method.

### Example 5:

``````s = {2,3,4,5}
t=("a","b")
print(s)``````

### Output :

``{2, 3, 4, 5, ('a', 'b')}``

### Example 6:

``````s = {2,3,4,5}
t=("a","b")
s.update(t)
print(s)``````

update function add a specified element into a set. But the position of adding an element depends upon the Python interpreter.

### Output (First run) :

``{2, 3, 4, 5, 'a', 'b'}``

### Output (Second run) :

``{2, 3, 4, 5, 'b', 'a'}``

### Output (Third run) :

``{2, 3, 4, 'a', 5, 'b'}``

As you can see, each time your set is updated.

## Adding a list in a Python set:

Important to note that list is added to the set only with the help of the update() method. Add a list with the help of add() method gives you an error.

### Example 7:

``````s = {2,3,4,5}
l=["a","b"]
s.update(l)
print(s)``````

### Output (First run) :

``{2, 3, 4, 5, 'b', 'a'}``

### Output (Second run) :

``{2, 3, 4, 5, 'a', 'b'}``

### Example 8:

``````s = {2,3,4,5}
l=["a","b"]
print(s)``````

### Output :

``````Traceback (most recent call last):
File "E:\Python files\kmtomile.py", line 31, in <module>