See Claude Code in Action

1. See Claude Code in Action

Hi, and welcome to this course on software development with Claude Code. I'm Dani, and I'll be your instructor for this course.

2. In This Course

Throughout the course, you'll use Claude Code to do four things: explore and understand an unfamiliar codebase, refactor legacy code, connect to an external database, and build a CLI tool from scratch. Let's look at two of those right now. First, exploring. Drop into a project you've never seen and ask Claude for an overview. Claude reads the whole project, not just one file, and gives you a map. That's your starting point for everything else. Now, let's ask what tables exist in the database and how the API uses them. Claude reasons across schema and routes and explains which endpoints consume this data. That's the real development cycle: describe what you need, review what Claude produces, and refine. Not a shortcut, a workflow. By the end of this course, that loop will feel natural.

3. Where Claude Code Fits

Let's zoom out for a second and see where Claude Code sits within the Anthropic ecosystem. Claude.ai is the browser chat interface. Claude Desktop adds local file access. Claude Code is built for development — terminal-native, with full project context and command execution. That's where we'll work.

4. Get Started

You don't need to install anything to follow along — all exercises run directly in the DataCamp platform. But if you want to use Claude Code on your own projects, install it with the command on screen. You'll need either a Claude Pro subscription or an Anthropic account with API access. Once installed, navigate to your project directory and run `claude` to launch it. Two commands you'll use constantly: `/clear` to reset the session, and `/exit` to quit. Run `/help` any time to browse the rest.

5. Navigating Confusing Code

Explanation is only half the picture, Claude can also work directly with your code. Here's a function that's doing something, but it's not obvious what. Single-letter variables, no comments, logic packed into one expression. This is the kind of code you inherit, not write.

6. Claude Explains and Documents

Let's ask Claude. And Claude delivers: threshold filtering, premium adjustment, value flagging, top-ten sort. Then with one follow-up, it adds a docstring. The change goes straight into the file. That's the pattern you'll use constantly: understand first, then improve.

7. Spotting a Bug

Here's a shorter function, but don't let that fool you. This function looks like it adds an item to a list. And it does, just not the way you'd expect. Can you spot the issue? It's one of Python's classic traps.

8. Claude Finds and Fixes the Bug

Let's ask Claude. Claude catches it immediately: mutable default argument. That list is created once at definition time, not per call; so state bleeds between calls. The fix is simple: default to None, initialize inside the function. Without help, this bug can take hours to find.

9. Troubleshooting

Before moving on, a few common issues worth knowing about. "Context window exceeded" means Claude's memory is full. Run /clear to reset. Rate limits are temporary; just wait and retry. And the deeper tip: vague prompts produce vague answers. Keep your requests focused on one task at a time, and you'll get much better results.

10. The Feedback Loop

That tip about focused prompts leads to something bigger: the core loop you'll use throughout this course. Describe what you need, review what Claude produces, test it, refine. You saw this in the demos earlier — explore first, then improve. The first response is rarely the last; iteration is the point. This pattern runs through every chapter: exploring the API, refactoring the code, connecting to the database, building the CLI.

11. Let's Practice!

Now it's your turn. Explore a codebase and fix a real issue with Claude Code. Let's go.

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