Running Your First Python Program

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Before You Begin

This guide assumes you have already installed Python on your computer. If you haven't, please follow one of our installation guides first:

• Standard Python Installation
• Windows only: Installing Python with Chocolatey

Creating Your First Python Program

Let's create a simple "Hello, World!" program - the traditional first program in any programming language.

Step 1: Open Your Text Editor

You can use any text editor to write Python code:

• Nano (command line): nano hello.py
• Notepad++ (Windows): Open Notepad++ and create a new file
• TextEdit (Mac): Open TextEdit, go to Format → Make Plain Text, then create a new file
• Thonny: Open Thonny and create a new file

Step 2: Write Your First Code

Type the following code in your text editor:

# This is my first Python program
print("Hello, World!")
print("Welcome to Python programming!")

# Let's make it interactive
name = input("What's your name? ")
print(f"Nice to meet you, {name}!")
  

What this code does:

• Lines starting with # are comments - notes for humans that Python ignores
• print() displays text on the screen
• input() gets text input from the user
• f"..." is a format string that lets you include variables in your text

Step 3: Save Your File

Save your file with a .py extension, which tells your computer it's a Python file. For example: hello.py

• In Nano: Press Ctrl+O, type the filename, and press Enter
• In other editors: Use File → Save or File → Save As

Step 4: Run Your Program

Now it's time to run your program! You'll need to use the command line for this.

On Windows:

1. Open Command Prompt or PowerShell
2. Navigate to the folder where you saved your file using the cd command

   cd path\to\your\folder

   For example, if your file is on the Desktop:

   cd C:\Users\YourUsername\Desktop

3. Run your program with Python:

   python hello.py

On Mac or Linux:

1. Open Terminal
2. Navigate to the folder where you saved your file:

   cd path/to/your/folder

   For example, if your file is on the Desktop:

   cd ~/Desktop

3. Run your program with Python:

   python3 hello.py

Step 5: See Your Program in Action!

When you run your program, you should see:

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

Type your name and press Enter. You should then see something like:

Nice to meet you, YourName!
  

Congratulations! You've just written and run your first Python program!

Understanding Your First Program

Line by Line Explanation

1. # This is my first Python program - This is a comment. Python ignores comments, but they help you understand your code
2. print("Hello, World!") - This prints the text "Hello, World!" to the screen
3. print("Welcome to Python programming!") - This prints another message
4. # Let's make it interactive - Another comment
5. name = input("What's your name? ") - This asks the user for their name and stores it in a variable called 'name'
6. print(f"Nice to meet you, {name}!") - This prints a message that includes the name the user entered

Key Concepts

• Functions like print() and input() are built-in commands that perform specific tasks
• Variables like name store information that you can use later
• Strings are text, usually enclosed in quotation marks
• f-strings (format strings) let you include variables inside text using {}

Try It Yourself: Modifying the Program

Now try making some changes to see how your program works:

Challenge 1: Add a Question

Modify your program to ask the user for their age too. Add these lines after the name input:

age = input("How old are you? ")
print(f"Wow, {age} is a great age to learn programming!")
  

Challenge 2: Create a Simple Calculator

Create a new file called calculator.py with this code:

print("Simple Calculator")
num1 = input("Enter the first number: ")
num2 = input("Enter the second number: ")

# Convert input strings to numbers
num1 = float(num1)
num2 = float(num2)

sum_result = num1 + num2
print(f"{num1} + {num2} = {sum_result}")
  

Run this program the same way you ran your first one!

What's Next?

Now that you've run your first Python program, you can:

• Learn more about Python basics in our lecture notes
• Try the W3Schools Python Tutorial for more exercises
• Explore more beginner Python projects at Real Python

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