How to Open a PY File

What is a PY file?

A .py file is a plain-text source file written in Python, one of the world's most widely used programming languages, created by Guido van Rossum and first released in 1991, now maintained by the Python Software Foundation. Being plain text, a .py file opens in literally any text editor — there's no special binary structure to it, the same way there isn't for a .txt file.

What makes a .py file useful is that it can be executed: a Python interpreter reads the file top to bottom and carries out the instructions it contains, whether that's printing text, doing calculations, processing data, or running a full application. That's the real reason "opening" a .py file usually means something different from opening a .pdf or a .jpg — you're not just viewing content, you're choosing whether to read it or run it.

How to run a PY file on Windows

1. Download and install Python from python.org, making sure to check "Add Python to PATH" during setup — this step trips up most first-time installs.
2. Open a terminal in the script's folder (Shift + right-click the folder, choose "Open PowerShell window here" or similar).
3. Run: python filename.py
4. The script's output appears directly in the terminal.

Double-clicking a .py file in File Explorer will also run it if Python is installed and associated with the extension, but the terminal method above lets you actually see any output or errors, which double-clicking usually doesn't.

How to run a PY file on Mac

1. Open Terminal (Applications > Utilities > Terminal).
2. Navigate to the script's folder: cd path/to/folder
3. Run: python3 filename.py

Modern macOS doesn't ship a full Python installation by default — if python3 isn't found, install it from python.org or via Homebrew: brew install python.

How to run a PY file on Linux

Most Linux distributions come with Python pre-installed. Open a terminal and run:

python3 filename.py

If it's not installed, get it with your package manager, e.g. sudo apt install python3 on Debian/Ubuntu, or sudo dnf install python3 on Fedora.

Which editor should I use?

For quick viewing, any text editor works. For actually writing or editing Python code, a dedicated editor makes a big difference:

• Visual Studio Code (free) — the most popular general-purpose editor, with an excellent Python extension.
• PyCharm (free Community edition available) — a full Python-specific IDE with deep debugging and refactoring tools.
• Jupyter Notebook — ideal for data science and step-by-step, cell-by-cell exploration rather than running a whole script at once.

Is it safe to run a .py file?

Only if you trust where it came from. Unlike opening a document or image, running a Python script means letting arbitrary code execute on your computer — it can read, modify or delete files, make network requests, or install other software, exactly like any other program. Read through the code first (or use the viewer above) if you're at all unsure, and never run a script downloaded from an untrusted source without understanding what it does.

Common PY file errors and how to fix them

"'python' is not recognized as an internal or external command" (Windows)

Python isn't in your system PATH. Reinstall from python.org with "Add Python to PATH" checked, or add the install folder to PATH manually.

"ModuleNotFoundError: No module named '...'"

The script imports a package that isn't installed. Install it with pip install packagename (matching the name shown in the error, which is sometimes different from the import name).

"SyntaxError" pointing at code that looks fine

Usually a Python version mismatch — the script was written for Python 2 (which uses different syntax for things like print) but you're running Python 3, or vice versa. Check which version the script expects.

"IndentationError"

Python uses indentation to define code blocks, so mixing tabs and spaces, or an inconsistent indent level, causes this. Most editors can auto-convert tabs to spaces to fix it.

Related file extensions

Frequently asked questions