Glossary

Plain-language definitions of terms you'll meet around here, A–Z.

Two fast ways to find a term

Use the search box (top right, or press /) to jump straight to a word — it searches the whole site. On wider screens, the contents list on the right of this page is a clickable alphabetical index.

Many of these terms also appear as dotted underlines in the lessons — hover (or tap) one for a quick definition in context.

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IDE

Integrated Development Environment — an editor bundled with tools to write, run, and debug code in one place (e.g., VS Code, PyCharm). IDLE is a tiny IDE; you'll graduate to a fuller one once the fundamentals are yours.

IDLE

Integrated Development and Learning Environment — the simple code editor and interactive shell that ships with Python. It's deliberately bare: no aggressive autocomplete or AI suggestions, which is exactly why it's good for learning. You write code, press F5, and it runs. We start here before any heavier tools. (It's also a nod to Monty Python's Eric Idle — Python is named after Monty Python's Flying Circus.)

Interpreter

The program that reads your Python code and runs it, line by line. When you "install Python," you're mainly installing the interpreter (the python / python3 command).

PATH

A list your operating system keeps of folders to search when you type a program's name. When a guide says "add Python to your PATH," it means "let me type python in a terminal and have the computer find it," instead of typing the program's full location every time. The classic Windows gotcha — "python is not recognized" — is almost always a PATH that wasn't set.

REPL

Read-Eval-Print Loop — an interactive prompt that reads a line of code, evaluates it, prints the result, and loops for the next line. Python's >>> prompt (including IDLE's shell) is a REPL: type 2 + 2, press Enter, see 4. Great for quick experiments. Not to be confused with Replit, a separate online IDE that happens to share the name.

Shell

A text prompt where you type commands — either your operating system's terminal (Command Prompt, PowerShell, Terminal) or a language shell like Python's >>> REPL.

Virtual environment (venv)

An isolated, per-project set of Python packages, so one project's installs can't clash with another's. You don't need one for an intro course (we use no third-party packages), but you'll meet them later.

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