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 you'll 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.
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
Common questions
- 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 it take?
- An hour to an hour and a half, in four short modules you can do at your own pace.
- 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.
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 one question per page, on up to five pages a day.
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've worked with data for about ten years, mostly at mission-driven organizations: policy research first, then education, and now early childhood services. 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