📂
STUDENT NOTES · DAY 13 OF 24
The Memory Chest 📂
Close your program and every variable vanishes. Files are the treasure chest where data survives.
1Writing your first file
🤖
Bittu: Variables live in my short-term memory — poof at shutdown. Files go on the DISK. They survive restarts, power cuts, everything.
🦉
Professor Hoot: The with block closes the file automatically when done. Always use it — no forgotten open files.
2Reading it back
3The three modes
📝 "w" write — wipes the file and starts fresh! ➕ "a" append — adds at the end 👀 "r" read — just looks
🐞
Bugly: Hehehe… open an important file with "w" by mistake and everything inside is GONE. My masterpiece.
4Reading a file that isn't there
🐍
Py: FileNotFoundError — read mode needs the file to exist. Tomorrow we learn to catch errors like this gracefully!
5Quick quiz! 🧠
You open an existing diary with open("diary.txt", "w"). What happens to the old entries?
💡 "w" erases and starts over. To add to the end, use "a" for append.
Why use with open(...) as f:?
💡 The with-block guarantees cleanup — the file closes even if something goes wrong inside.
6Your mission 🚀
Mission 1: Write your 3 favourite movies to movies.txt, one per line.
Mission 2: Read the file back and print each line with a loop.
Mission 3: Append a 4th movie with "a" mode, re-read, and confirm all 4 are there.
Day 13 done — your programs have memory now! 💾
Next: exception handling — programs that survive mistakes instead of crashing.
Go to Day 14: Error Shields →