🐍 Chapter 4: Programming in Python

SEE Computer Science 2083 - CDC New Curriculum. This chapter covers Python basics, user defined functions, libraries, graphics, file handling and data visualization.

🐍 Python 📘 Theory 💻 Practical 🚀 Project Work

📌 On This Page

• 4.1 Revision of Basics of Python
• 4.2 User Defined Functions
• 4.3 Modules, Packages and Libraries
• 4.4 Graphics Using Turtle
• 4.5 Error Handling
• 4.6 File Handling Using Pandas
• 4.7 Data Visualization
• Practical Tasks
• Project Work

4.1 Revision of Basics of Python

Introduction to Python

Python is a high-level, interpreted and general-purpose programming language. It is popular because of its simple syntax and easy readability.

Features of Python

• Simple and easy to learn.
• High level programming language.
• Interpreted language.
• Portable and platform independent.
• Supports object oriented programming.
• Provides large number of libraries.

Input and Output Statements

Input and Output statements are used to communicate with users. Input receives data and output displays results.

print() Statement

The print() function is used to display output on the screen.

print("Hello Python")

Output:

Hello Python

input() Function

The input() function is used to receive data from the user.

name = input("Enter your name: ")

print(name)

Output:

Enter your name: Ram

Ram

Data Types in Python

A data type defines the type of value stored in a variable.

Data Type	Description	Example
int	Whole numbers	10
float	Decimal numbers	10.5
str	Text/String	"Python"
bool	True or False	True

Variables in Python

A variable is a named memory location used to store data.

Example:

name = "Hari"

age = 16

marks = 90

Rules for Naming Variables

• Must start with a letter or underscore.
• Cannot start with a number.
• No spaces are allowed.
• Python keywords cannot be used.
• Variable names are case sensitive.

Operators in Python

Operator	Name
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus
**	Power

Expressions

An expression is a combination of variables, values and operators that produces a result.

Examples:

10 + 5

a * b

x > y

Conditional Statements

Conditional statements are used to make decisions according to conditions.

if Statement

age = 18

if age >= 18:
    print("Eligible")

if-else Statement

age = 15

if age >= 18:
    print("Adult")

else:
    print("Child")

if-elif-else Statement

marks = 80

if marks >= 90:
    print("A")

elif marks >= 60:
    print("B")

else:
    print("C")

Loops in Python

Loops are used to repeat a block of code multiple times.

for Loop

for i in range(5):

    print(i)

while Loop

i = 1

while i <= 5:

    print(i)

    i = i + 1

⭐ SEE Exam Tips

• input() always returns string data.
• = is assignment operator.
• == is comparison operator.
• % gives remainder.
• Indentation is compulsory in Python.

4.2 User Defined Functions

What is a Function?

A function is a block of organized and reusable code that performs a specific task. Functions help divide large programs into smaller and manageable parts.

Advantages of Functions

• Code reusability.
• Reduces repetition of code.
• Makes programs easier to understand.
• Improves program organization.
• Makes debugging and maintenance easier.

Types of Python Functions

Function Type	Description
Built-in Functions	Functions already available in Python. Examples: print(), input(), len(), sum()
User Defined Functions	Functions created by programmers according to their requirements.

Creating a User Defined Function

User defined functions are created using the def keyword.

Syntax

def function_name(parameters):

    statements

    return value

Example: Function without Parameter

def welcome():

    print("Welcome to Python")


welcome()

Output:

Welcome to Python

Function Call

A function call is the process of executing a function by writing its name followed by parentheses.

Example:

def greet():

    print("Hello")


greet()

Parameters and Arguments

Parameters

Parameters are variables written inside the function definition. They receive values when the function is called.

Example:

def add(a,b):

    print(a+b)

Here:

a and b are parameters

Arguments

Arguments are actual values passed to a function during function call.

Example:

add(10,20)

Here:

10 and 20 are arguments

Difference Between Parameter and Argument

Parameter	Argument
Written in function definition	Written during function call
Receives values	Passes values
Example: a,b	Example: 10,20

Scope of Variables

Scope defines the area where a variable can be accessed in a program.

1. Local Scope

A variable created inside a function is called a local variable. It can only be used inside that function.

Example:

def show():

    x = 10

    print(x)


show()

2. Global Scope

A variable created outside a function is called a global variable. It can be accessed throughout the program.

Example:

x = 20


def display():

    print(x)


display()

Return Statement

The return statement sends a value back from a function to the calling program.

Syntax:

return value

Example:

def square(n):

    return n*n


result = square(5)


print(result)

Output:

25

Types of Arguments

1. Positional Arguments

Arguments are passed in the same order as parameters.

Example:

def student(name,age):

    print(name,age)


student("Ram",16)

2. Default Arguments

A default argument has a predefined value.

Example:

def greet(name="Student"):

    print(name)


greet()

greet("Hari")

Output:

Student

Hari

3. Keyword Arguments

In keyword arguments, values are passed using parameter names.

Example:

def info(name,age):

    print(name,age)


info(age=16,name="Ram")

Functions Returning Values

A function that returns a result using return statement is called a non-void function.

Example:

def addition(a,b):

    return a+b


print(addition(5,3))

Output:

8

Void Functions

A function that performs a task but does not return any value is called a void function.

Example:

def message():

    print("Hello Python")


message()

Returning Multiple Values

Python allows a function to return multiple values separated by commas.

Example:

def calculate(a,b):

    return a+b, a-b


x,y = calculate(10,5)


print(x)

print(y)

Output:

15

5

⭐ SEE Exam Tips

• Function is created using def keyword.
• Parameters are written in function definition.
• Arguments are passed during function call.
• return sends result back to caller.
• Local variables cannot be accessed outside function.

4.2 User Defined Functions

What is a Function?

A function is a block of organized and reusable code that performs a specific task. Functions help divide large programs into smaller and manageable parts.

Advantages of Functions

• Code reusability.
• Reduces repetition of code.
• Makes programs easier to understand.
• Improves program organization.
• Makes debugging and maintenance easier.

Types of Python Functions

Function Type	Description
Built-in Functions	Functions already available in Python. Examples: print(), input(), len(), sum()
User Defined Functions	Functions created by programmers according to their requirements.

Creating a User Defined Function

User defined functions are created using the def keyword.

Syntax

def function_name(parameters):

    statements

    return value

Example: Function without Parameter

def welcome():

    print("Welcome to Python")


welcome()

Output:

Welcome to Python

Function Call

A function call is the process of executing a function by writing its name followed by parentheses.

Example:

def greet():

    print("Hello")


greet()

Parameters and Arguments

Parameters

Parameters are variables written inside the function definition. They receive values when the function is called.

Example:

def add(a,b):

    print(a+b)

Here:

a and b are parameters

Arguments

Arguments are actual values passed to a function during function call.

Example:

add(10,20)

Here:

10 and 20 are arguments

Difference Between Parameter and Argument

Parameter	Argument
Written in function definition	Written during function call
Receives values	Passes values
Example: a,b	Example: 10,20

Scope of Variables

Scope defines the area where a variable can be accessed in a program.

1. Local Scope

A variable created inside a function is called a local variable. It can only be used inside that function.

Example:

def show():

    x = 10

    print(x)


show()

2. Global Scope

A variable created outside a function is called a global variable. It can be accessed throughout the program.

Example:

x = 20


def display():

    print(x)


display()

Return Statement

The return statement sends a value back from a function to the calling program.

Syntax:

return value

Example:

def square(n):

    return n*n


result = square(5)


print(result)

Output:

25

Types of Arguments

1. Positional Arguments

Arguments are passed in the same order as parameters.

Example:

def student(name,age):

    print(name,age)


student("Ram",16)

2. Default Arguments

A default argument has a predefined value.

Example:

def greet(name="Student"):

    print(name)


greet()

greet("Hari")

Output:

Student

Hari

3. Keyword Arguments

In keyword arguments, values are passed using parameter names.

Example:

def info(name,age):

    print(name,age)


info(age=16,name="Ram")

Functions Returning Values

A function that returns a result using return statement is called a non-void function.

Example:

def addition(a,b):

    return a+b


print(addition(5,3))

Output:

8

Void Functions

A function that performs a task but does not return any value is called a void function.

Example:

def message():

    print("Hello Python")


message()

Returning Multiple Values

Python allows a function to return multiple values separated by commas.

Example:

def calculate(a,b):

    return a+b, a-b


x,y = calculate(10,5)


print(x)

print(y)

Output:

15

5

⭐ SEE Exam Tips

• Function is created using def keyword.
• Parameters are written in function definition.
• Arguments are passed during function call.
• return sends result back to caller.
• Local variables cannot be accessed outside function.

4.4 Graphics Using Turtle

Introduction to Turtle Module

The Turtle module is a built-in Python module used to create graphics by drawing lines, shapes and designs using a cursor called a turtle.

It is mainly used for learning programming in a simple and visual way.

Uses of Turtle Module

• Helps learn programming through graphics.
• Makes programming interactive and interesting.
• Helps understand loops, functions and angles.
• Improves creativity and logical thinking.
• Makes errors easier to identify visually.

Basic Structure of Turtle Program

import turtle

pen = turtle.Turtle()

# Turtle commands

turtle.done()

Explanation of Commands

Command	Description
import turtle	Imports turtle module into the program.
turtle.Screen()	Creates drawing window.
turtle.Turtle()	Creates turtle object.
turtle.done()	Keeps drawing window open.

Turtle Motion Commands

Command	Purpose	Example
forward()	Moves turtle forward	pen.forward(100)
backward()	Moves turtle backward	pen.backward(50)
right()	Turns clockwise	pen.right(90)
left()	Turns anticlockwise	pen.left(90)
circle()	Draws circle	pen.circle(50)

Color and Style Commands

Command	Purpose
color()	Changes pen color
fillcolor()	Sets filling color
pensize()	Changes pen thickness
speed()	Controls drawing speed

Pen Control Commands

penup()

Lifts the pen and stops drawing.

Example:

pen.penup()

pen.forward(100)

pen.pendown()

pendown()

Places the pen down and starts drawing.

Position Commands

Command	Purpose
goto(x,y)	Moves turtle to specific position.
home()	Returns turtle to starting position.
heading()	Shows current direction.

Fill Commands

pen.begin_fill()

# drawing commands

pen.end_fill()

These commands fill closed shapes with colour.

Screen Commands

Command	Purpose
clear()	Removes drawings.
reset()	Clears screen and resets turtle.
hideturtle()	Hides turtle cursor.
showturtle()	Shows turtle cursor.
bgcolor()	Changes background colour.

Common Turtle Shapes

Shape	Example
arrow	pen.shape("arrow")
turtle	pen.shape("turtle")
circle	pen.shape("circle")
square	pen.shape("square")
triangle	pen.shape("triangle")

Solved Turtle Programs

1. Draw a Straight Line

import turtle

pen = turtle.Turtle()

pen.forward(200)

turtle.done()

2. Draw a Square

import turtle

pen = turtle.Turtle()


for i in range(4):

    pen.forward(100)

    pen.right(90)


turtle.done()

3. Draw a Rectangle

import turtle

pen=turtle.Turtle()


for i in range(2):

    pen.forward(150)

    pen.right(90)

    pen.forward(80)

    pen.right(90)


turtle.done()

4. Draw a Triangle

import turtle

pen=turtle.Turtle()


for i in range(3):

    pen.forward(120)

    pen.left(120)


turtle.done()

5. Draw a Circle

import turtle

pen=turtle.Turtle()

pen.circle(80)

turtle.done()

⭐ SEE Exam Tips

• Turtle starts from center position (0,0).
• Square turning angle = 90°.
• Triangle turning angle = 120°.
• Circle is drawn using circle() command.
• begin_fill() and end_fill() are used for colouring shapes.

4.5 Error Handling

Introduction

Error handling is the process of detecting and handling errors during program execution so that the program does not crash suddenly.

Importance of Error Handling

• Prevents program crashes.
• Makes programs reliable.
• Displays meaningful error messages.
• Improves debugging.
• Increases software quality.

Types of Errors in Python

Error Type	Description
Syntax Error	Error caused by violation of Python syntax rules. Example: Missing colon.
Runtime Error	Error occurring during program execution. Example: Division by zero.
Logical Error	Program runs but gives incorrect output.

Exception Handling

Exception handling is used to handle runtime errors using:

• try
• except
• else
• finally

try Block

The try block contains code that may produce an error.

except Block

The except block handles the error.

else Block

The else block executes when no error occurs.

finally Block

The finally block always executes whether error occurs or not.

Example of Exception Handling

try:

    a = int(input("Enter number:"))

    b = int(input("Enter number:"))

    result = a/b

    print(result)


except ZeroDivisionError:

    print("Cannot divide by zero")


finally:

    print("Program completed")

Common Python Exceptions

Exception	Meaning
ZeroDivisionError	Division by zero
ValueError	Wrong value entered
TypeError	Wrong data type
IndexError	Invalid index
FileNotFoundError	File does not exist

4.6 File Handling Using Pandas Library

Introduction

File handling is the process of storing data permanently in files and accessing that data when required.

File Handling Modes

Mode	Purpose
r	Read file
w	Write file
a	Append data

Pandas Library

Pandas is a Python library used for data handling and analysis. It uses DataFrame structure to store data.

Reading CSV File

import pandas as pd


data = pd.read_csv("student.csv")


print(data)

Writing CSV File

import pandas as pd


data = {

"Name":["Ram","Hari"],

"Age":[15,16]

}


df = pd.DataFrame(data)


df.to_csv("student.csv")

Advantages of Pandas

• Easy data handling.
• Reads CSV and Excel files.
• Provides DataFrame structure.
• Useful for data analysis.

4.7 Introduction to Data Visualization

Data visualization is the process of representing data in graphical form so that information can be understood easily.

Matplotlib Library

Matplotlib is a Python library used to create charts and graphs.

Types of Charts

1. Line Chart

A line chart shows changes in data over time.

Example:

import matplotlib.pyplot as plt


x=[1,2,3]

y=[4,5,6]


plt.plot(x,y)

plt.show()

2. Bar Graph

Bar graphs compare values between different categories.

Example:

import matplotlib.pyplot as plt


names=["A","B","C"]

marks=[80,90,70]


plt.bar(names,marks)

plt.show()

3. Pie Chart

Pie charts show percentage distribution of data.

Example:

import matplotlib.pyplot as plt


data=[40,30,20,10]


plt.pie(data)

plt.show()

Practical Tasks

• Demonstrate structure of user defined functions.
• Install and use Python packages and libraries such as Pandas, Turtle and Matplotlib.
• Draw different shapes using Turtle graphics.
• Read and write CSV files using Pandas.
• Create bar, line and pie charts using Matplotlib.

Project Work

Develop a simple Python project using:

• User defined functions.
• Python libraries.
• Data visualization tools.

Project Report Should Include

• Introduction of project.
• Problem definition.
• Tools and libraries used.
• Development process.
• Program code.
• Output screenshots.
• Conclusion.