Part 47 · Module 7: Modules, the Standard Library and Packages

Lesson 2: Numbers, chance and real dates from the standard library

16 min read·14 Oct 2026

Module 7 · Lesson 2 · About 50 minutes · Needs: Module 7 Lesson 1 (import and from ... import), Module 6 (functions, return, assert), Module 5 (lists and dictionaries)

The situation

Amira has stopped counting shelf days. "Use real dates," she says. "Jonah does not know what day 44 is. He knows it is Wednesday."

Until now you counted shelf days by hand. This lesson hands the counting to Python. You will follow Jonah's loan L04, Frankenstein, borrowed on Monday 14 September 2026, to a real "16 days late" on Wednesday 14 October 2026, picking up rounding and repeatable random choices on the way.

Shelf day 44 (grey, the old way) becomes a real date (blue, your code's normal path) that knows its weekday, month lengths and leap years.

The situation

The rest of this part opens with an account