Intro to Python

Your First Python Program

Python turns a plain-text file into running instructions, and the first useful instruction almost every program shares is printing text to the screen.

Variables and Types

A variable is a name Python attaches to a value, and the type of that value decides what the program is allowed to do with it.

Numbers and Math

Python does more than add and subtract: floor division, modulo, and exponents cover most of the math a real program needs, and knowing which operator gives an int versus a float saves a class of bugs.

Working with Strings

Text in Python lives in a string, and a string comes with its own toolkit: joining, formatting, cleaning, and picking apart characters by position.

Getting Input from the User

The input() function hands back a string no matter what was typed, and skipping the conversion to a number is the single most common beginner bug in Python.

Making Decisions with if

A Python program reads its input, compares values with booleans, and uses if, elif, and else to run different code depending on what it finds.

Repeating with Loops

A for loop repeats a fixed number of times over a range or a sequence, and a while loop repeats for as long as a condition holds, with break and continue changing how a single pass ends.

Lists: Many Values in One

A list holds many values under one name and in one order, and indexing, slicing, and looping are how a program reaches in and gets exactly what it needs.

Writing Functions

A function names a piece of logic once so a program can call it by that name instead of retyping the same lines everywhere they're needed.

Build a Small Program

A number-guessing game pulls every piece from this module, variables, strings, numbers, conditionals, loops, lists, and a function, into one program that actually runs.