Think in Python / CORE PATH

Variables, types & missing values

A name refers to an object; type determines the operations that object supports.

3h planning budget · Sohila Khaled Abbas · Reviewed 2026-11-01

Compare Python None with SQL NULL, and distinguish missingness from zero and an empty string.

Understand the idea

A name refers to an object; type determines the operations that object supports. Compare Python None with SQL NULL, and distinguish missingness from zero and an empty string.

Work through the practice with a tiny fixture, predict the result before running it, and record one boundary case. Use the exit check as evidence before moving on.

What to learn

Use str, int, float, bool and None deliberately.
Convert text at input boundaries and inspect types.
Use integer minor units for these EGP exercises: 100 piastres = 1 EGP.

A small original example

from decimal import Decimal
amount = Decimal("12.50")
piastres = int(amount * 100)
print(piastres)  # 1250; validate precision before int in real input code

Practice on your own data

Task 02: convert a decimal EGP string to integer piastres; reject fractions below one piastre.

Practice this lesson in the Python lab →

EXIT CHECK

"12.50" becomes 1250; "0.001" and "NaN" raise ValueError.

Common pitfalls

bool("False") is True because the string is nonempty.
Binary floats are unsuitable for exact currency equality.

Prerequisites

Run a program

Boot.dev chapter 2 · 15:02 ↗

Video and playlist companions

Choose one explanation for the concept, then attempt the practice. These are topic mappings, not a claim that every linked lesson covers every outcome.