Your First Python Program & The Interactive Shell

Now that everything's installed, let's actually write some Python. And to be honest with you — this is where the real fun begins.

We're going to do two things in this tutorial:

1. Play with Python's interactive shell — type code, get instant results
2. Write and run a proper Python program — the classic "Hello, World!"

Table of Contents

• The Python Interactive Shell
• Your First Python Program
• Let's Make It More Interesting
• Interactive Shell vs Running a File
• Common Mistakes (And How to Fix Them)
• Try This Challenge

The Python Interactive Shell

What Is It?

The Python interactive shell (also called REPL — Read, Evaluate, Print, Loop) is like having a conversation with Python. You type something, and Python replies immediately. No saving files, no running scripts. Just you and Python, talking back and forth.

How to Launch It

Open your terminal (Command Prompt, Terminal, or PowerShell) and just type:

python

If that doesn't work, try:

py

Or on some systems:

python3

You should see something like this:

Python 3.13.2 (tags/v3.13.2:...)
Type "help", "copyright", "credits" or "license" for more information.
>>>

Those three arrows >>> are Python's way of saying "I'm ready. What do you want?"

Let's Play

Go ahead and type this, then press Enter:

>>> print("Hello, World!")

And just like that, Python responds:

Hello, World!

Now try some math — Python doubles as a calculator:

>>> 2 + 2
4

>>> 10 * 5
50

>>> 7 ** 2
49

>>> (10 + 5) * 2
30

Feels instant, right? That's the beauty of the REPL. Every line you type is executed immediately.

Variables in the Shell

You can also store values and use them later:

>>> name = "Alice"
>>> print(name)
Alice

>>> age = 25
>>> age + 5
30

A Handy Trick — The _ Variable

Here's something most beginners don't know: in the interactive shell, the underscore _ stores the last result.

>>> 15 + 7
22
>>> _ * 2
44

Exiting the Shell

When you're done playing, type:

>>> exit()

Or press Ctrl+Z then Enter on Windows, or Ctrl+D on Mac/Linux.

Your First Python Program

Alright, the interactive shell is fun for quick experiments. But real programs live in files.

Step 1: Create a Python File

Open VS Code and create a new file:

• Press Ctrl+N to create a new file
• Press Ctrl+S to save it
• Name it hello.py

The .py extension tells everyone (and every program) that this is a Python file.

Step 2: Write Your First Program

Type this into the file:

print("Hello, World!")

That's it. One line. You've just written a complete Python program.

Step 3: Run It

You have a few ways to run this:

Method 1 — VS Code Run Button Look at the top-right corner of the editor. See that little triangle "Run" button? Click it. Your program runs, and the output appears in a terminal panel at the bottom.

Method 2 — Right-Click (My Favorite) Right-click anywhere in the code and select "Run Python File in Terminal". Quick and easy.

Method 3 — Terminal Open the terminal in VS Code (Ctrl+`` ) and type:

python hello.py

You Should See:

Hello, World!

That's it. You've written and run your first Python program. Take a moment — seriously. You just took the first step into programming.

Let's Make It More Interesting

One line is cool, but let's write something with a bit more personality:

# This is a comment — Python ignores this line
# It's for humans to read

name = input("What's your name? ")
print(f"Nice to meet you, {name}!")
age = input("How old are you? ")
print(f"Wow, {age} years old! You're young at heart.")

Save this as greet.py and run it. Here's what happens:

What's your name? Rohan
Nice to meet you, Rohan!
How old are you? 25
Wow, 25 years old! You're young at heart.

Notice a few things:

• input() waits for you to type something and press Enter
• f"..." is an f-string — it lets you put variables inside your text
• Lines starting with # are comments (Python ignores them)
• One thing to remember: input() always gives you a string, even if you type a number. So age is text like "25", not the number 25. We'll talk more about this when we get to data types.

Interactive Shell vs Running a File

Let's clear up the difference because it confuses a lot of beginners:

Think of it this way: The interactive shell is like a notepad where you scribble quick notes. A .py file is like a proper document you save and share.

Common Mistakes (And How to Fix Them)

Forgetting Quotes

print(Hello)  # Error!
print("Hello")  # Correct

Python thinks Hello is a variable name, not text. Always put text in quotes.

Mixing Quote Types

print("Hello')  # Error!

You started with a double quote but ended with a single quote. Pick one and stick with it. Both "..." and '...' work, just don't mix them.

Forgetting Parentheses

print "Hello"  # Error (in Python 3)
print("Hello")  # Correct

In Python 3, print is a function. Functions need parentheses.

Wrong Indentation

print("Hello")
  print("World")  # Unexpected indent

Python is picky about spacing at the start of lines. Don't add random spaces or tabs.

Try This Challenge

Write a program that:

1. Asks for your favorite movie
2. Asks for the year it was released
3. Prints a sentence combining both

Here's a template to get you started:

movie = input("What's your favorite movie? ")
year = input("What year was it released? ")
print(f"...")  # You fill in the rest

When you run it, it should look like:

What's your favorite movie? The Matrix
What year was it released? 1999
The Matrix was released in 1999! Great choice.