Every variable we'd worked with for four weeks held exactly one thing.

One name. One score. One balance. One grade.

That's fine for simple programs. But real data doesn't come in ones. A school has hundreds of students. A shop has thousands of products. M-Pesa processes millions of transactions every day.

I opened Week 5 with a question: "How do you store 500 student names in Python?"

Someone said: name1 = "Amina", name2 = "Brian" ...