What you'll learn in this Python file i/o tutorial

This interactive Python tutorial has 7 hands-on exercises. Estimated time: 16 minutes.

1. Writing a file — To create a file, open it in write mode (`"w"`) and call `.write()`.
2. Reading a file — `open(file, "r")` opens for reading. `.read()` gets the entire content as one string.
3. Read line by line — For large files, reading everything at once wastes memory. Instead, loop through the file — Python reads one line at a t…
4. Append mode — don't overwrite — `"w"` mode erases the file first. `"a"` mode adds to the end — like writing in a journal.
5. Why `with` matters — What if your code crashes before you close the file? The data might not get saved.
6. Process a CSV manually — CSV files are just text with commas. You already know `.split()` — that's all you need.
7. Build a word counter 📊 — Write a program that: