Why Your CSV Looks Wrong: Garbled Accents, Semicolons, Lost Zeros and Dates
By the end you'll be able to read any CSV without breaking its accents, decimals, codes or dates, and hand one over that opens correctly on the other end.
You go at your own pace, with your Maestro beside you, 1:1, through the whole course: ask it anything, and it asks you questions too.
15 skills · 4 modules
What will you be able to do?
Each box is a skill. The base is at the bottom, recognizing and explaining, and you work your way up to building something of your own and judging what works and why. Hover over a box to see what it builds on. Click it to see where I teach it and how your Maestro checks it.
- Analyze
- Apply
- Understand
Analyze
Diagnose what is wrong with a CSV that looks broken and how to fix it
Where I teach it: Open, export and hand off without surprises · How do I fix a CSV that has every problem at once?
Builds on:
- Explain how garbled accents (Mérida) and the � diamond come about
- Read postal codes, IDs and invoice numbers as text
- Tell when scientific notation is only a display and when digits were lost
- Read dates by stating their format instead of letting the program guess
- Identify a file's delimiter, decimal mark and thousands separator
Your Maestro asks you to break a problem down with it and saves it as evidence when you do.
Apply
Identify a file's delimiter, decimal mark and thousands separator
Where I teach it: What's inside a CSV · What is inside a CSV file?
Builds on:
- Explain that a CSV is only text, with no types or formats
- Explain why a CSV uses semicolons where the comma is the decimal mark
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Repair text that was already saved with broken accents
Where I teach it: What's inside a CSV · How does "Mérida" turn into "Mérida"?
Builds on:
- Explain how garbled accents (Mérida) and the � diamond come about
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Read UTF-8 files with a BOM without it leaking into the first column
Where I teach it: Commas, semicolons and the BOM · What is a BOM, and why does my first column have extra characters?
Builds on:
- Explain what an encoding is and why one letter can take one or two bytes
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Read a CSV in pandas stating the separator, decimals, encoding and types
Where I teach it: Commas, semicolons and the BOM · How do I read a file from another country correctly in pandas?
Builds on:
- Identify a file's delimiter, decimal mark and thousands separator
- Explain how garbled accents (Mérida) and the � diamond come about
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Read postal codes, IDs and invoice numbers as text
Where I teach it: Zeros, long numbers and dates · Why do CSV files lose leading zeros?
Builds on:
- Explain that a CSV is only text, with no types or formats
- Read a CSV in pandas stating the separator, decimals, encoding and types
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Read dates by stating their format instead of letting the program guess
Where I teach it: Zeros, long numbers and dates · Is 03/04/2026 March 4 or April 3?
Builds on:
- Read a CSV in pandas stating the separator, decimals, encoding and types
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Understand
Explain that a CSV is only text, with no types or formats
Where I teach it: What's inside a CSV · Why does my CSV look wrong?
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain how garbled accents (Mérida) and the � diamond come about
Where I teach it: What's inside a CSV · Why does my CSV look wrong?
Builds on:
- Explain what an encoding is and why one letter can take one or two bytes
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain what an encoding is and why one letter can take one or two bytes
Where I teach it: What's inside a CSV · What is UTF-8, and why does an "é" take two bytes?
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain why a CSV uses semicolons where the comma is the decimal mark
Where I teach it: Commas, semicolons and the BOM · Why does my CSV use semicolons?
Builds on:
- Explain that a CSV is only text, with no types or formats
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Tell when scientific notation is only a display and when digits were lost
Where I teach it: Zeros, long numbers and dates · Why does my barcode show up as 7.501235e+12?
Builds on:
- Explain that a CSV is only text, with no types or formats
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Who is this course for?
For anyone who receives, opens and sends CSV files at work and runs into garbled accents, semicolons instead of commas, disappearing zeros or codes in scientific notation. You don't need to know how to program: the exercises come with code, and you change one or two lines. It's also useful if you only use Excel.
Ask your Maestro
Your Maestro is an AI that knows this course. Ask it about the first page and it answers right here, free.
You: Where do I start?
Your Maestro: From what you already know. Tell me what you've done with data, and I'll start this page from there.
Asking about: Answers from the page "Why does my CSV look wrong?"
Only this browser keeps what you ask here. How it works
What we'll cover
What's inside a CSV
Commas, semicolons and the BOM
Zeros, long numbers and dates
Open, export and hand off without surprises
How long does it take?
1 to 1.5 hours
A guide: you go at your own pace, and the course waits where you left off.
Common questions
- Why does my CSV show broken accents?
- A CSV is just text, and accents break when a program reads it with a different encoding than the one used to save it. The course explains how those odd characters appear, how to read the file with the right encoding in pandas, and what the BOM does so Excel opens it correctly.
- Why does Excel remove my leading zeros?
- Because Excel reads a code like 00123 as a number and drops the zeros. The data in the CSV is fine, the problem is how it is opened. In the course you learn to read those columns as text, protect long numbers, and import and export in Excel without losing the format.
- Do I need to know how to program?
- No. The exercises come with the code already written; you change a line or two and see what happens. Python, pandas and DuckDB run on the course page, so there's nothing to install.
- Is it useful if I only use Excel?
- Yes. Every problem is explained first as text and bytes, and module 4 teaches importing and exporting in Excel, on Windows and on Mac, with the steps Microsoft gives in its help pages.
- How long does the course take?
- Between one hour and an hour and a half, in four short modules you do at your own pace. You can do it in one sitting or one module at a time. Everything runs on the course page with nothing to install, and the sample files stay there: you upload none of your work files anywhere.
- What happens to my work files?
- You don't upload them anywhere. The course uses sample files, and if you describe what you see, your Maestro helps you find the page that covers your case.
- Do I need a course, or can I learn this on my own?
- You can learn it on your own, and many people do. A course gives you the order: what to practice first, ready-to-use data, and exercises that show where you go wrong before it happens at work. This course is free, and your Maestro answers questions as you go. If you prefer going solo, the method still works.
How do I check what AI does? I teach it in Your AI and Your Data: Don't Let It Make Up the Number and Check what AI gives you in three steps.
What you get
- 4 modules and 14 pages, open whenever you want them.
Open to everyone: read all of it, and your Maestro, an AI, answers your questions on every page.
With a free account: your Maestro for the whole course, always on the page you're on, and the exercises run with nothing to install.
Who's teaching you
Sergio Sánchez
I'm Sergio, chekos online. I'm a data architect, and I've spent more than ten years working with data in the Bay Area, mostly at mission-driven organizations: policy research first, then education, and now early childhood services. I grew up in Tijuana. In 2018 I started tacosdedatos to share what I was learning, and since then it's been a blog, a podcast, courses, guides, and a community. These days I spend a lot of my time building with AI agents and writing about how I organize my work around them. I share what I've learned; you take what's useful and make it yours.
See you in the course
Why Your CSV Looks Wrong: Garbled Accents, Semicolons, Lost Zeros and Dates