Your First Automation

Reading about automation is not the same as running automation.

This section is different from everything before it. There is nothing to study here. There is only one thing to do: run a real Python script that solves a real problem.

By the end of this page, you will have:

• Asked Claude Code to write a Python script
• Run that script on actual files
• Seen files renamed automatically
• Handled an error (we're going to manufacture one so you learn the repair workflow)

This takes about 20 minutes. No shortcuts.

The Task

You have 20 PDF files in a folder. Someone sent them to you with random names. You need them renamed to a numbered, sequential format — padded to 3 digits so they sort correctly: Invoice_001.pdf before Invoice_010.pdf before Invoice_020.pdf.

Normally: open each file, right-click, rename, type the new name. Twenty times. Roughly 10 minutes if you're fast.

We will do all 20 in under 2 seconds.

Step 1: Create Test Files

We need test files to work with. We will create them using the command prompt so you don't need to find 20 real PDFs.

Step 2: Open Claude Code

Step 3: Give Claude Code the Prompt

Type this prompt exactly. Do not paraphrase — be precise:

"Write a Python script that renames all PDF files in C:\Users[YourUsername]\Desktop\first-automation\test-invoices. Rename them to Invoice_001.pdf, Invoice_002.pdf, up to Invoice_020.pdf — padded to 3 digits. Before making any changes, show me a preview list of every old name to new name pair. Only proceed after I type 'yes'."

Step 4: What Claude Will Generate

Claude Code will produce a Python script. Read through it before running and find these three things:

1. The folder path — confirm it matches your actual path
2. The preview section — the code that prints old name to new name pairs
3. The confirmation check — the code that waits for you to type yes

If any of these three are missing, ask Claude to add them before you save the script.

Step 5: Save the Script

Claude Code may have already created the file for you. If not:

You should see rename_invoices.py in the list.

Step 6: Run the Script

Twenty files. Named correctly. Under 2 seconds of actual work.

Step 7: Handling an Error (The Repair Workflow)

Every developer, at every skill level, encounters errors. The question is not "will I get errors" — the answer is yes. The question is "what do I do when I get one."

Let's see a real error and fix it.

The files were already renamed in Step 6. So if you run the script again, it will try to rename Invoice_001.pdf to Invoice_001.pdf (no change needed). A well-written script handles this gracefully — it detects that the files are already in the right format and either skips them or reports them.

Step 8: What to Do When Claude's Code Has a Real Error

Sometimes — not often, but sometimes — Claude generates code that doesn't work as expected. Here is the exact repair workflow:

If the script crashes with a Python error (a "traceback"):

Copy the entire error message. Go back to Claude Code. Paste it and say: "I ran the script and got this error. Fix it." Claude will explain what went wrong and give you the corrected code.

If the script runs but produces wrong output:

Say: "The script ran but renamed the files incorrectly — it produced [describe what you see] instead of [describe what you expected]. Fix the renaming logic."

If you're not sure what it did or what went wrong:

Say: "The script ran but I'm not sure if it did the right thing. Walk me through what it did step by step and tell me if anything went wrong."

The key insight: you are not debugging Python. You are describing symptoms to Claude, and Claude fixes the Python. Your job is to notice when the output is wrong and describe it accurately.

What Just Happened

Stop and register what you just did.

You had a folder with 20 chaotically named PDF files. You asked Claude Code to write a script in plain English. You read the script at a high level and understood what it was doing. You ran it. You saw a preview. You confirmed. The files were renamed — all 20 — in under 2 seconds.

The next time you have 500 files to rename, you now know the workflow:

The next time you have a folder of Excel files to combine, you know the workflow. The next time you need to validate a list of GST numbers, you know the workflow. The next time you need to send 200 client emails from a spreadsheet, you know the workflow.

The workflow is always the same. Only the task changes.

Taking This Further

The script you just ran is a starting point. Here are natural next steps — each one is a single Claude Code prompt away:

Add logging to a file: Instead of just printing what happened, write the results to a log file so you have a record of every run. Ask Claude: "Extend the script to write the results to a log file called rename_log.txt with the timestamp and the old/new names."

Read filenames from an Excel sheet: Instead of numbering sequentially, use a column in Excel to specify exactly what each file should be renamed to. Ask Claude: "Modify the script to read target filenames from column B of rename_list.xlsx, where column A is the current filename."

Run automatically on a schedule: Windows Task Scheduler can run a Python script at a set time — every Monday morning, every month on the 1st, etc. Ask Claude: "Write instructions for scheduling this script to run every Monday at 8am using Windows Task Scheduler."

Ask Claude Code for any of these extensions. Claude will extend the script. You run it. The capability grows.

Module Complete

You have finished the Power of Code module.

• You controlled your computer with words
• You saw Python eliminate hours of manual work in seconds
• You ran your first real automation
• You learned the repair workflow for when things go wrong

Everything from here — React, Supabase, building web apps — is built on this foundation. Code is precise instructions that computers follow exactly. You now feel what that means.

The next module: AI Basics — understanding tokens, context windows, and how to give Claude Code the most powerful instructions possible.