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Functions, Strings, and
8 Lists in Python

Pre-Processing
Pre-Processing
• Functions in Python • Features of Functions
• Components of a Python Function • Types of Functions in Python
• Creating a Function • Calling a Function
• Working with Strings • Working with Lists

A complex and large program can be broken down into simpler and manageable parts of codes
called modules. One type of programming modules is called Functions.

FUNCTIONS IN PYTHON
A Function is a code block that has a name and can be reused anywhere in a program. A function
performs a specific task. It can be used in a program by simply using its name. The print( ) and input( )
are examples of functions that you have already used in various programs in Python.

FEATURES OF FUNCTIONS
Functions are the basic components of a procedural programming language. Some important fea-
tures of functions are:
1. Modularity: Functions let us divide a large, complex program into small parts called modules.
This helps in keeping the code organised and easy to make changes in it.
2. Reusability: A function can be used as many times as required in a program. This saves time
and effort of writing the same code repeatedly. It also helps reduce the length of a program.
3. Easy Debugging: It is easy to track errors in a program and correct them when it is divided into
smaller, manageable segments.

COMPONENTS OF A PYTHON FUNCTION
A Python program is made up of the following components:
• Function Name: A function is given a name that is unique and related to its purpose.
• Arguments: The values given as input to the function are called Arguments. A function may or
may not have any arguments.
• Body of Function: It consists of all the executable statements that are used to perform the task
of the function.
• Return Expression: A function may or may not return a value as output.

For example, consider the code for a function given below:
def area_square(side):
area = side * side
return area
Here, the name of the function is area_square. It accepts one argument – side. It calculates the area
of the square. The value of area is returned by the return statement.

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