**Video link:** [https://youtu.be/n4B3zYfk_Pg](https://youtu.be/n4B3zYfk_Pg)

**Video link:**

In this video, we learned about Python functions that make our program more organized and manageable by dividing our code into smaller and modular chunks.

**Programs in the Video**

- [Python Functions](#python-functions-1)

- [Function Arguments](#function-arguments)

- [Passing Multiple Arguments](#passing-multiple-arguments)

- [Return Value from Function](#return-value-from-function)

- [**Example**: Grading Students](#example)

- [**Task**: Function to Add and Multiply](#programming-task)

A function is a group of related statements that performs a specific task.

For example,

def greet():

print("Hello")

print("How do you do?")

Here, we have defined a function named `greet`.

To create a function, we use the `def` keyword followed by the function name, parenthesis `()`, and a colon `:`.

The body of the function is specified using indentation.

When we run the program, we don't see any output.

It is because defining a function won't do anything. To bring the function into action, we need to call it.

def greet():

print("Hello")

print("How do you do?")

greet()

**Output**

One advantage of defining a function is that we can call it any number of times.

def greet():

print("Hello")

print("How do you do?")

greet()

greet()

greet()

**Output**

Also, we need to define a function first before we can call it.

The following code gives an error:

greet()

def greet():

print("Hello")

print("How do you do?")

When the `greet()` function is called, Python doesn't know that this function exists because it's defined after the function call.

Suppose we want to make our `greet()` function a bit more personal.

Instead of printing `Hello`, we want to print something like `Hello Jack` or whatever the person's name is.

For this, we can use function arguments:

def greet(name):

print("Hello", name)

print("How do you do?")

greet("Jack")

**Output**

Function arguments are passed inside the parenthesis during the function call.

It can then be accessed using the `name` parameter in the function definition.

If we need to pass multiple arguments to a function, we can separate them by commas.

Let's create a function to add two numbers.

def add_numbers(n1, n2):

result = n1 + n2

print("The sum is", result)

number1 = 5.4

number2 = 6.7

add_numbers(number1, number2)

**Output**

We have passed `number1` and `number2` as arguments to the `add_numbers()` function.

These arguments are accepted as `n1` and `n2` once they are passed to the `add_numbers()` function.

def add_numbers(n1, n2):

result = n1 + n2

print("The sum is", result)

add_numbers(5.4, 6.7)

Sometimes it's better just to find the sum inside the function and print the result somewhere else.

We can achieve that by using the `return` statement.

def add_numbers(n1, n2):

result = n1 + n2

return result

result = add_numbers(5.4, 6.7)

print("The sum is", result)

**Output**

There are two types of functions:

- **Built-in functions** - Functions that are built into Python.

- **User-defined functions** - Functions defined by the users themselves.

Some built-in functions:

|Function|Description|

|---|---|

|`float()`|converts to decimal number and returns it|

|`int()`|converts to integer and returns it|

|`input()`|function to take input from the user|

Suppose you just attended a University examination. The marks you obtained in various subjects are stored in a list like this:

marks = [55, 64, 75, 80, 65]

**You want to find the average marks you obtained in the exam.**

**Based on the average marks you want to find your grade as:**

- **You will get Grade A if the average marks is equal to or above 80**

- **You will get Grade B if the average marks is equal to or above 60 and less than 80**

- **You will get Grade C if the average marks is equal to or above 50 and less than 60**

- **And if the average marks is less than 50, you will get Grade F**

def find_average_marks(marks):

sum_of_marks = sum(marks)

number_of_subjects = len(marks)

average_marks = sum_of_marks/number_of_subjects

return average_marks

def compute_grade(average_marks):

if average_marks >= 80.0:

grade = 'A'

elif average_marks >= 60:

grade = 'B'

elif average_marks >= 50:

grade = 'C'

else:

grade = 'F'

return grade

marks = [55, 64, 75, 80, 65]

average_marks = find_average_marks(marks)

grade =compute_grade(average_marks)

print("Your average marks is", average_marks)

print("Your grade is", grade)

**Output**

**Can you create a program to add and multiply two numbers?**

**For this, create two functions `add_numbers()` and `multiply_numbers()`.

These functions should compute the result and return them to the function call and should print from outside the function.**

def add_numbers(num1, num2):

return num1 + num2

def multiply_numbers(num1, num2):

return num1 * num2

number1 = 5

number2 = 30

num_sum = add_numbers(number1, number2)

print("Sum is", num_sum)

num_product = multiply_numbers(number1, number2)

print("Product is", num_product)

**Output**