Installing Python

To write real programs, you’ll want Python on your own computer. This lesson walks you through installing it on Windows, macOS and Linux, running code in two different ways, and setting up a good free editor.

Step 1: Download and install#

Windows#

1. Go to python.org/downloads and click the big Download Python 3.x button.
2. Run the installer.
3. Important: tick “Add python.exe to PATH” at the bottom of the first screen. Without it, typing python in the terminal won’t work.
4. Click Install Now.

Python is also available in the Microsoft Store, which sets up the PATH automatically.

macOS#

1. Download the macOS installer from python.org/downloads and run it.
2. Or, if you use Homebrew: brew install python.

macOS may include an older system Python used by the operating system. Always use the one you installed, with the command python3.

Linux#

Most distributions already include Python 3. If not:

sudo apt install python3 python3-pip python3-venv   # Ubuntu / Debian
sudo dnf install python3                            # Fedora

Step 2: Check it works#

Open a terminal (Windows: search for Terminal or Command Prompt; macOS: Terminal) and type:

python --version

On macOS and Linux, use python3:

python3 --version

You should see something like Python 3.13.1. Any version from 3.10 upward works for this course. If you see “command not found” or a Microsoft Store window on Windows, reinstall and make sure “Add to PATH” is ticked.

From here on, we’ll write python; use python3 if that’s what works on your computer.

Way 1: The interactive shell (REPL)#

Type python alone and press Enter:

>>> 2 + 2
4
>>> "hello".upper()
'HELLO'
>>> name = "Asha"
>>> f"Hi {name}"
'Hi Asha'
>>> exit()

The >>> prompt means Python is waiting for a line. It runs each line immediately and shows the result. This is called a REPL (Read–Eval–Print Loop) and is perfect for quick experiments: “what does this function return?”. Type exit() (or press Ctrl+D on macOS/Linux, Ctrl+Z then Enter on Windows) to leave.

Way 2: Python files#

Real programs live in files ending in .py. Create a folder, for example python-course, and a file inside it called hello.py:

name = input("What's your name? ")
print(f"Nice to meet you, {name}!")
print("You just ran your first Python file.")

In the terminal, go to the folder and run it:

cd python-course
python hello.py

Type your name when asked. input() waits for the user to type something and press Enter.

Step 3: Set up an editor (VS Code)#

You can write Python in any text editor, but a code editor helps a lot. Visual Studio Code (VS Code) is free and the most popular choice:

1. Download it from code.visualstudio.com and install it.
2. Open VS Code → Extensions (the squares icon on the left) → search Python → install the one by Microsoft.
3. File → Open Folder → choose your python-course folder.
4. Open hello.py and click the ▶ Run button in the top-right corner.

The output appears in the built-in terminal at the bottom. The Python extension also gives you:

• Colour highlighting and error underlines as you type.
• Autocomplete for functions and variables.
• A debugger to run code step by step.

PyCharm Community (free) is another excellent Python-specific editor.

Step 4 (optional): Jupyter notebooks#

Data scientists often use notebooks: documents that mix code, results, charts and notes. You can try them with no installation at colab.research.google.com (Google Colab), or in VS Code with the Jupyter extension. They’re great for experiments; for programs and scripts, .py files are better.

Where pip fits in#

Python comes with pip, a tool for installing extra packages (libraries others have written):

python -m pip --version

You’ll use it in the “pip and Packages” lesson. For now, just check that this command prints a version.

Troubleshooting#

Problem	Fix
'python' is not recognized (Windows)	Reinstall with “Add python.exe to PATH” ticked, or use py instead of python
python opens the Microsoft Store	Use py, or turn off the “App execution aliases” for python in Windows settings
command not found: python (Mac/Linux)	Use python3
VS Code runs the wrong Python	Press Ctrl+Shift+P → “Python: Select Interpreter” → choose the version you installed
can't open file 'hello.py'	You’re in the wrong folder; use cd to go to the folder containing the file

Common mistakes#

• Forgetting “Add to PATH” on Windows.
• Typing Python code into the terminal without starting python first (or the reverse: typing python hello.py inside the >>> shell).
• **Saving files as hello.py.txt** with Notepad. Use a code editor.
• Naming your file after a module, like random.py or math.py. It hides Python’s own module of that name and causes confusing errors.

Exercise#

1. Install Python and check the version in the terminal.
2. In the REPL, calculate 2 ** 100 (Python handles very big numbers).
3. Create age.py that asks for the user’s birth year with input() and prints their approximate age. (Hint: int(input(...)) converts the answer to a number; you’ll learn why in lesson 5.)
4. Install VS Code with the Python extension and run age.py from it.

Summary#

• Install Python 3 from python.org; on Windows, tick “Add python.exe to PATH”.
• Check with python --version (or python3).
• The REPL (>>>) runs lines instantly; .py files hold real programs: python file.py.
• VS Code with the Python extension is a great free editor.

Next, you’ll learn the basic syntax rules of Python.