Python Fundamentals

Your First Python Program

A Python program is just a list of instructions, followed in order, top to bottom — like a recipe. Let's write and understand your very first one.

Variables & Data Types

A variable is just a labeled box that holds a value — you can look inside it, use what's inside, or put something new in later.

Making Decisions & Repeating Things

This is where that "indentation matters" note from lesson one finally makes sense — it's exactly how Python shows what belongs inside a decision or a loop.

Functions: Naming a Set of Steps

A function is a named, reusable chunk of instructions — write it once, then just call its name whenever you need those steps again.

Organizing Data: Lists & Dictionaries

A list is an ordered row of items, like a numbered shelf. A dictionary is a set of labeled values, like a filing cabinet with named folders.

Modules, pip, and Virtual Environments

You almost never write everything from scratch — import lets you reuse code someone else already wrote, and pip is how you get hold of it.

Reading and Writing Files

Every program so far has forgotten everything the moment it stops running. Files are how a program remembers something for next time — write it down now, read it back later.

Handling Errors Gracefully with try/except

Things go wrong — a file might not exist, someone might type text where a number was expected. try/except lets your program handle that gracefully instead of crashing outright.

Working with JSON and API-Style Data

Almost every web service on the internet speaks JSON. Python's json module translates effortlessly between JSON text and Python's own dictionaries and lists.

Classes and Objects: Bundling Data and Behavior

A class is a blueprint for creating objects that carry their own data around with them, along with the actions that work on that data.

Working with Dates and Times

Almost every real program eventually needs to know "what day is it" or "how long until then" — Python's datetime module handles the surprisingly fiddly math for you.