Your First Python Program

Welcome to your first Python programming lesson! In this tutorial, you'll learn how to write and run your very first Python program. Don't worry if you're completely new to programming - we'll start simple and build from there.

The Classic "Hello, World!"

Every programming journey begins with the traditional "Hello, World!" program. It's a simple program that displays a message on the screen.

Writing the Code

Open your text editor or Python IDE and type the following:

print("Hello, World!")

That's it! You've written your first Python program. Let's break it down:

print() is a built-in Python function that displays text on the screen
The text inside the parentheses and quotes is called a "string"
The quotes (either single ' or double ") tell Python that this is text, not code

Running Your Program

Method 1: Using the Command Line

Save your file as hello.py (the .py extension tells your computer it's a Python file)
Open your terminal or command prompt
Navigate to where you saved the file
Type: python hello.py and press Enter

Method 2: Using Python's Interactive Mode

Open your terminal
Type python (or python3 on some systems) and press Enter
You'll see the Python prompt: >>>
Type your code directly: print("Hello, World!")
Press Enter to see the result

Understanding the Output

When you run the program, you should see:

Hello, World!

Congratulations! You've successfully run your first Python program.

Let's Make It More Interesting

Now let's create a more interactive program that asks for your name:

# This is a comment - Python ignores this line
name = input("What's your name? ")
print("Hello, " + name + "!")
print("Welcome to Python programming!")

New Concepts Explained

Comments: Lines starting with # are comments. They help explain your code but don't run
Variables: name is a variable that stores the user's input
input(): This function asks the user to type something
String concatenation: The + operator joins strings together

Running the Interactive Program

Save this as greet.py and run it. You'll see something like:

What's your name? Alice
Hello, Alice!
Welcome to Python programming!

A Slightly More Complex Example

Let's create a simple calculator:

# Simple Calculator
print("=== Simple Calculator ===")

# Get two numbers from the user
num1 = float(input("Enter the first number: "))
num2 = float(input("Enter the second number: "))

# Perform calculations
addition = num1 + num2
subtraction = num1 - num2
multiplication = num1 * num2
division = num1 / num2

# Display results
print("\nResults:")
print(f"Addition: {num1} + {num2} = {addition}")
print(f"Subtraction: {num1} - {num2} = {subtraction}")
print(f"Multiplication: {num1} * {num2} = {multiplication}")
print(f"Division: {num1} / {num2} = {division}")

New Concepts

float(): Converts text input to a decimal number
Mathematical operations: +, -, *, / for basic math
f-strings: The f"" syntax is a modern way to insert variables into strings
\n: Creates a new line in the output

Understanding Python Syntax

Python has some unique characteristics:

Indentation Matters

Unlike many programming languages that use curly braces {}, Python uses indentation to group code:

# This will work
if True:
    print("This is indented")
    print("This is also indented")

# This will cause an error
if True:
print("This is not indented correctly")

Case Sensitivity

Python is case-sensitive, meaning Print and print are different:

print("This works")    # Correct
Print("This doesn't")  # Error - capital P

Common Beginner Mistakes

1. Forgetting Quotes

# Wrong
print(Hello, World!)

# Correct
print("Hello, World!")

2. Mixing Quote Types

# Wrong
print("Hello, World!')

# Correct
print("Hello, World!")  # or print('Hello, World!')

3. Forgetting Parentheses

# Wrong
print "Hello, World!"

# Correct
print("Hello, World!")

Practice Exercises

Try these exercises to reinforce what you've learned:

Exercise 1: Personal Information

Write a program that asks for your name, age, and favorite color, then displays them in a formatted message.

Exercise 2: Simple Math

Create a program that asks for a number and displays its square (the number multiplied by itself).

Exercise 3: Temperature Converter

Write a program that converts Celsius to Fahrenheit using the formula: F = (C × 9/5) + 32

Sample Solutions

Exercise 1 Solution:

name = input("Enter your name: ")
age = input("Enter your age: ")
color = input("Enter your favorite color: ")

print(f"Hi {name}! You are {age} years old and your favorite color is {color}.")

Exercise 2 Solution:

number = float(input("Enter a number: "))
square = number * number
print(f"The square of {number} is {square}")

Exercise 3 Solution:

celsius = float(input("Enter temperature in Celsius: "))
fahrenheit = (celsius * 9/5) + 32
print(f"{celsius}°C is equal to {fahrenheit}°F")

Debugging Tips

When your program doesn't work as expected:

Read error messages carefully - they often tell you exactly what's wrong
Check your spelling - prnit instead of print won't work
Check your quotes and parentheses - make sure they match
Use print statements to see what's happening in your code

What's Next?

You've successfully written and run your first Python programs! You've learned about:

The print() function
Variables and user input
Basic string operations
Comments
Simple mathematical operations

Next Steps:

Key Takeaways

Python is designed to be readable and simple
The print() function displays output
Variables store information
Indentation is important in Python
Practice makes perfect!

Remember: Every expert programmer started with "Hello, World!" Don't worry if things seem confusing at first - programming is a skill that improves with practice.