Stage 1 · Lesson 3 of 7
Files, collections and errors
Most real programs do three things: they keep data in collections, save and load it from files, and cope when something goes wrong. Learn your language's list (or ), (or hash map) and set. A list keeps items in order, a dictionary pairs a key with a value, and a set holds each item only once.
A dictionary turns "find the student with this roll number" from a loop over every student into one quick lookup. Then read and write text and files (plain files with commas between the values). Finally, handle errors with try and except (try and catch in Java or C++), so a missing file or a bad number gives a clear message instead of a crash.
Courses often skip , but it is what separates a lab exercise from a program someone else can use.
A question to check yourself, an AI practice session and 3 cheat sheet entries come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking Python Fundamentals
Design Gurus · Beginner · $50
If Python is your language: short lessons with an in-browser exercise after each one
- CourseFreeCS50: Introduction to Computer Science
Harvard University · Beginner
The free course your first year should have been: C, memory, then Python, with hard problem sets