Introduction to Python | Basics of Python Programming | Complete Notes | CBSE Class 11 Informatics Practices (2026–27)
Class 11 · Informatics Practices
Introduction to Python | Basics of Python Programming
Python is one of the world's most popular programming languages. It is widely used in education, web development, artificial intelligence, data science, automation, cybersecurity, and software development. Python is known for its simple syntax, readability, and ease of learning, making it an ideal programming language for beginners.
What is Python?
Python is a high-level, interpreted, general-purpose programming language that enables programmers to write simple, readable, and efficient programs.
Python follows an easy-to-understand syntax similar to the English language, allowing beginners to learn programming concepts quickly.
History of Python
Python was developed by Guido van Rossum in the late 1980s at Centrum Wiskunde & Informatica (CWI), Netherlands. The first official version, Python 0.9.0, was released in 1991.
The name "Python" was inspired by the British comedy television series Monty Python's Flying Circus and not by the snake.
Features of Python
| Feature | Description |
|---|---|
| Simple | Easy to read and write. |
| Interpreted | Programs are executed line by line. |
| High-Level | Focuses on programming rather than hardware details. |
| Portable | Runs on Windows, Linux, and macOS with minimal changes. |
| Open Source | Available free of cost. |
| Object-Oriented | Supports object-oriented programming concepts. |
| Large Standard Library | Provides many built-in modules and functions. |
Why Learn Python?
- Easy for beginners.
- Simple and readable syntax.
- Used in many industries.
- Excellent community support.
- High demand in the job market.
- Supports multiple programming paradigms.
Applications of Python
| Field | Examples |
|---|---|
| Web Development | Django, Flask |
| Data Science | NumPy, Pandas |
| Artificial Intelligence | Machine Learning, Deep Learning |
| Automation | Task Automation, Scripting |
| Game Development | Simple games using Python libraries |
| Cyber Security | Security testing and automation |
| Education | Teaching programming concepts |
Installing Python
To start programming in Python, download and install the latest stable version from the official Python website.
- Download Python.
- Run the installer.
- Select Add Python to PATH.
- Complete the installation.
- Open Python IDLE.
Python IDLE
IDLE (Integrated Development and Learning Environment) is the default environment provided with Python. It allows users to write, edit, save, and execute Python programs.
Features of IDLE
- Interactive Shell
- Script Editor
- Syntax Highlighting
- Automatic Indentation
- Debugging Support
Execution Modes in Python
Python programs can be executed in two different modes.
1. Interactive Mode
In Interactive Mode, Python executes each statement immediately after it is entered.
Advantages
- Quick testing.
- Immediate output.
- Useful for beginners.
Example
>>> 5 + 3
8
>>> print("Hello")
Hello
2. Script Mode
In Script Mode, Python programs are written in a file with the .py extension and executed together.
Advantages
- Suitable for larger programs.
- Programs can be saved.
- Easy to edit and reuse.
Example
print("Welcome to Python")
print("CBSE Class 11")
Interactive Mode vs Script Mode
| Interactive Mode | Script Mode |
|---|---|
| Statement-by-statement execution | Entire program execution |
| Output immediately | Output after running the program |
| Cannot save programs easily | Programs are saved as .py files |
| Best for testing | Best for developing applications |
Structure of a Python Program
A Python program consists of one or more statements written in a logical sequence. It may include comments, variables, input statements, processing, and output statements.
Example
# Program to calculate sum
num1 = 20
num2 = 30
total = num1 + num2
print("Sum =", total)
Your First Python Program
Program
print("Hello, World!")
Output
Hello, World!
Real-Life Applications
| Application | Python Usage |
|---|---|
| Online Shopping | Website development |
| Banking | Automation and reporting |
| Education | Learning programming |
| Artificial Intelligence | Machine learning applications |
| Scientific Research | Data analysis |
Common Errors
| Mistake | Correct Concept |
|---|---|
| Python is a compiled language. | Python is an interpreted language. |
| Interactive Mode saves programs automatically. | Programs should be saved separately in Script Mode. |
| Python only works on Windows. | Python runs on multiple operating systems. |
| Python is only used for web development. | Python is used in AI, Data Science, Automation, Web Development, Education, and many other fields. |
Quick Revision
| Concept | Remember |
|---|---|
| Developer | Guido van Rossum |
| Released | 1991 |
| Language Type | High-level, interpreted |
| Execution Modes | Interactive and Script |
| IDLE | Integrated Development and Learning Environment |
| File Extension | .py |
CBSE Exam Tips
- Remember the two execution modes and their differences.
- Know the full form of IDLE.
- Be able to explain why Python is considered beginner-friendly.
- Practice writing and running simple Python programs.
- Understand the basic structure of a Python program.
Summary
Python is a simple, powerful, and versatile programming language widely used across different industries. Its easy syntax, portability, and extensive library support make it one of the most popular programming languages for beginners and professionals alike. Python programs can be executed using Interactive Mode or Script Mode, and Python IDLE provides a convenient environment for writing and running programs. Learning these basics builds a strong foundation for studying variables, operators, control statements, lists, dictionaries, and NumPy in later chapters.