Fundamentals. Everything you need before line 21.

The input/process/output model that every program — from a calculator to a cloud platform — is built on. Plus the development loop you'll spend your career in.

The four types you'll use 95% of the time (str, int, float, bool), the rules for naming variables, and the type-conversion bugs that bite every beginner.

Arithmetic, modulo, exponents, floor division, and the floating-point trap. Where to use modulo in real code. Why you should never store money in a float.

Quotes, escape sequences, f-strings, indexing, slicing, immutability, and the 8 string methods that handle 95% of real text work.

if / elif / else, comparison operators, and / or / not, truthiness rules, and two refactors that flatten ugly conditional chains.

How to stop repeating yourself. def, parameters vs arguments, return values, default values, the mutable-default trap, and local scope.

Reading tracebacks, syntax errors vs runtime exceptions, try/except/else/finally, the five exceptions you'll see most, and when to catch vs let it crash.