Setting Up the Python Environment

Before writing any Python code, you need Python itself installed, a way to confirm it is working correctly, and an editor or IDE that makes writing and running scripts comfortable. Unlike compiled languages, Python code can also be run interactively, line by line, which is one of the fastest ways to experiment with the language while learning it.

This lesson covers installing Python from python.org or a version manager, verifying the install from the terminal, choosing an editor, running a script as a file, and using the interactive REPL (Read-Eval-Print Loop) for quick experimentation.

Why it matters

A surprising number of early problems are not about code at all: the wrong Python version runs, a package installs into a different interpreter, or the command is not found. Knowing how to check which interpreter you are using and how to run a file removes these problems before they waste your time.

Installing Python

The most direct route is downloading an installer from python.org for your operating system; on Windows, be sure to check "Add python.exe to PATH" during installation, since forgetting this is the single most common setup mistake. On macOS and Linux, Python 3 is often preinstalled or available via the system package manager, but many developers instead use a version manager such as pyenv, which lets you install and switch between multiple Python versions cleanly — important because different projects may require different Python versions.

• python.org installer — simplest for a single, system-wide Python install.
• pyenv (macOS/Linux) or pyenv-win (Windows) — lets you install and switch between several Python versions per project.
• Package managers (Homebrew on macOS, apt on Ubuntu) — convenient but can lag behind the latest Python release.

Verifying the Installation

After installing, open a terminal and run python --version (or python3 --version on systems where "python" still points to Python 2 or nothing at all). This should print something like Python 3.12.4. If the command is not found, the installation did not add Python to your system PATH, and you will need to either reinstall with that option checked or add the install directory manually.

Choosing an Editor or IDE

Visual Studio Code with the official Python extension is a popular lightweight choice: it adds syntax highlighting, linting, debugging, and an integrated terminal, and it works well whether you are writing a ten-line script or a large project. PyCharm (from JetBrains) is a full-featured Python-specific IDE with deeper refactoring tools, a built-in debugger, and strong support for frameworks like Django, at the cost of being heavier to run. Either is a reasonable starting point; the important thing is having integrated run/debug support so you are not constantly switching between an editor window and a separate terminal.

Running a Script vs. the Interactive REPL

A Python script is a plain text file ending in .py, executed from the terminal with python filename.py; this is how real programs are run. The REPL, started by typing just python with no filename, gives you an interactive prompt (>>>) where you type one expression or statement at a time and see its result immediately — ideal for testing a small piece of syntax, inspecting an object, or checking how a function behaves, without creating a file at all. Many editors also offer an integrated interactive console that behaves the same way.

Example

# Terminal: verify installation
$ python --version

# hello.py
print("Hello from a Python script")

# Terminal: run the script file
$ python hello.py

# Terminal: interactive REPL session
$ python
>>> 2 + 2
>>> name = "Webnest"
>>> print(f"Hello, {name}!")
>>> exit()

Python 3.12.4
Hello from a Python script
>>> 4
>>> Hello, Webnest!

Exercise

Write a script that prints the major version number of the Python that is running it, and then whether that Python is version 3.8 or newer.

Expected output: 3 then True

import sys

# TODO: print the major version number
# TODO: print whether the version is at least 3.8

import sys

print(sys.version_info.major)
print(sys.version_info >= (3, 8))

Quick quiz

Interview questions