When you launch IDLE, you begin in shell mode, which is simply a Python Read-Evaluate-Print-Loop (REPL) similar to what you get when you type python in a terminal window.
Take a look at the shell mode in the following screenshot:
IDLE's shell has some nice features that you don't get from the command-line REPL, like syntax highlighting and tab-completion. The REPL is essential to the Python development process, as it gives you the ability to test code in real time and inspect classes and APIs without having to write complete scripts. We'll use the shell mode in later chapters to explore the features and behaviors ...
