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FollowtheDamnCode

Python from zero

Learn to program from zero with Python — short, readable code that runs as soon as you write it. The language of scripting, automation, data, and machine learning, and the easiest first language to read. The whole course is free.

1Getting Started

What a program is, how Python runs it, and your first lines of output.

  1. What Is a Program?Instructions for a computer — and how Python runs them.
  2. Running PythonThe interactive shell, scripts, and why indentation matters.
  3. print()Showing text and numbers, with sep, end, and escape sequences.
  4. CommentsNotes in your code that Python ignores.

2Variables & Types

Storing values — numbers, text, True/False, and None — and reading them from the user.

  1. VariablesNames that refer to values.
  2. Numbersint and float — whole numbers and decimals.
  3. StringsText in quotes — joining, repeating, and measuring it.
  4. Booleans and NoneTrue, False, truthiness, and the value that means "nothing".
  5. Type ConversionTurning text into numbers and numbers into text.
  6. Reading Inputinput(), and turning what the user typed into numbers.

3Operators

Maths, comparisons, and combining True/False answers.

  1. Arithmetic Operators+, -, *, /, //, %, and **.
  2. Comparison and Logical Operators==, <, >, and, or, not.
  3. Shortcuts and Precedence+=, and which operator goes first.

4Strings

Getting at characters, transforming text, and formatting it beautifully.

  1. Indexing and SlicingGetting one character, or a piece, by position.
  2. String Methodsupper, strip, replace, split, join, and friends.
  3. f-stringsDropping values into text, and formatting numbers.

5Control Flow

Making decisions and repeating work — if, loops, and match.

  1. if, elif, elseRunning code only when a condition is True.
  2. while LoopsRepeating while a condition stays True.
  3. for Loops and rangeGoing through items one at a time, and counting.
  4. break and continueLeaving a loop early, or skipping one round.
  5. match and casePicking a branch by matching a value against patterns.

6Collections

Holding many values at once — lists, tuples, sets, and dictionaries — and building them in one line.

  1. ListsOrdered, changeable collections — and why b = a doesn't copy.
  2. TuplesFixed groups of values, and unpacking them.
  3. SetsUnique values, fast membership, and Venn-diagram maths.
  4. DictionariesLooking values up by key.
  5. ComprehensionsBuilding lists, sets, and dicts in one line.

7Functions

Naming a piece of work once and using it everywhere — parameters, return values, scope, lambdas, and recursion.

  1. Functionsdef, calling, and why functions exist.
  2. Parameters and returnPassing values in, getting results back, and default values.
  3. *args and **kwargsFunctions that take any number of arguments.
  4. ScopeLocal and global names, and where Python looks them up.
  5. LambdasTiny one-line functions, and sorting by a key.
  6. RecursionFunctions that call themselves.

8Errors

Reading tracebacks, catching exceptions, and raising your own.

  1. Exceptions and TracebacksWhat happens when code fails, and how to read the report.
  2. try, except, else, finallyHandling errors instead of crashing.
  3. Raising ExceptionsSignalling problems from your own code.

9Files & Modules

Saving data to files, splitting code into modules, and a tour of the standard library.

  1. Reading and Writing Filesopen, with, and file modes.
  2. Modules and Importsimport, from-import, and your own modules.
  3. The Standard Librarymath, random, datetime, collections, and itertools.

10Classes & Objects

Bundling data with the code that uses it — classes, inheritance, dunder methods, and dataclasses.

  1. Classes and ObjectsBlueprints, __init__, self, and methods.
  2. InheritanceChild classes, overriding, and super().
  3. Dunder MethodsMaking objects print, add, and compare.
  4. DataclassesData-holding classes without the boilerplate.

11Pythonic Idioms

The habits that make Python code short and clear — enumerate, zip, unpacking, generators, and decorators.

  1. enumerate and zipPositions and parallel lists, without range(len(...)).
  2. UnpackingSplitting sequences into names, with *rest.
  3. Iterators and Generatorsyield, laziness, and how for loops really work.
  4. DecoratorsWrapping functions to add behaviour.