Comparing Shell and REPL: Key Differences Explained

Hi everybody 👋

In this article, I try to explain the difference between a Shell and a REPL.

Initially, I was planning to write an article on “Python in Shell”, but while learning, I found myself asking ChatGPT about the difference between a Shell and a REPL. That’s when I realized this confusion might not be unique to me. So I felt it would be helpful to first write an article explaining the difference between Shell and REPL, in case someone else gets stuck in a similar situation.

So, let’s break it down.

A REPL is a type of shell, but not all shells are REPLs.

Shells are primarily used to run system or OS-level commands. However, we cannot directly run system commands inside a REPL.

On the other hand, REPLs are designed to run code written in a specific programming language—for example, the Python REPL.

You also cannot run Python code directly inside a shell. To do that, you must first enter the Python REPL from the shell.

Examples of shells include:

Windows Command Prompt (CMD)

Windows PowerShell

Terminal on macOS or Linux

So essentially, a REPL exists inside a shell.

For example, inside the terminal or shell in VS Code, when you type:

python on Windows

python3 on macOS

you enter the Python REPL, where the cycle of Read, Evaluate, Print, and Loop happens.

Analogy

Think of it this way:

A Shell is like a room

A REPL is like a chair inside that room

You must first enter the room, and only then can you sit on the chair and do your work (which, in this case, is writing and executing code).

In short

A Shell runs operating system commands

A REPL runs programming language code

That’s the core difference.