# Python From Zero

Python is the language people reach for when they want to *get something done* without fighting the
language first - data work, scripts, web backends, automation, glue between systems. It reads almost
like English, which makes it inviting, and that same readability hides a few sharp edges nobody warns
you about. This guide takes you the whole way: from "I've never run Python" to understanding what the
language is *actually doing* underneath your code - explaining each piece rather than handing you spells
to memorize.

It's one zero-to-hero journey in two halves. **Phases 1–9 are the basics** - enough to write real,
well-organized programs. **Phases 10–18 are the deep half** - the data model, generators, decorators,
typing, concurrency, performance, and packaging, the stuff that separates "writes Python" from
"understands Python." Each phase carries a difficulty badge so you can see the climb.

If programming itself is brand new - not just Python - start with
[Programming From Zero](/guides/programming-from-zero) first; it builds the "what is a program" mental
model this guide assumes.

## How to read this
- **Brand new to Python?** Read 1–9 in order, top to bottom - each builds on the last. Type the examples
  as you go (most are runnable right here); doing beats reading. Come back for 10+ when the basics feel
  comfortable.
- **Already know another language?** Skim 1–5 for Python's spelling of ideas you have, then start properly
  at [Phase 6: Objects & Classes](06-objects-and-classes.md).
- **Past the basics already?** Jump straight to the deep half - [Phase 10: The Data Model](10-the-data-model.md)
  onward is where Python stops being "a readable scripting language" and starts being a language you can
  reason about to the metal.

## The phases

**Part 1 - The basics (🟢 Basic → 🟡 Intermediate)**
1. **[Install & Your First Program](01-install-and-first-program.md)** 🟢 - Python 3, the REPL, a real `hello.py`.
2. **[Syntax, Values & Types](02-syntax-values-and-types.md)** 🟢 - indentation as structure, the core types, f-strings.
3. **[Collections](03-collections.md)** 🟢 - lists, tuples, dicts, sets, and the aliasing trap.
4. **[Control Flow & Functions](04-control-flow-and-functions.md)** 🟢 - `if`/loops/`def`, truthiness, the mutable-default trap.
5. **[Modules & Project Layout](05-modules-and-project-layout.md)** 🟢 - `import`, the stdlib, `__main__`, a clean layout.
6. **[Objects & Classes](06-objects-and-classes.md)** 🟡 - what an object really is, `self`, when to reach for a class.
7. **[Errors & I/O](07-errors-and-io.md)** 🟡 - reading tracebacks, `try`/`except`, files without corruption.
8. **[Ecosystem & Tooling](08-ecosystem-and-tooling.md)** 🟡 - `pip`, virtual environments, formatters, linters.
9. **[Idioms & Gotchas](09-idioms-and-gotchas.md)** 🟡 - the Pythonic way, and the sharp edges that bite everyone once.

**Part 2 - Beyond the basics (🔴 Advanced)**
10. **[The Data Model & Dunder Methods](10-the-data-model.md)** 🔴 - make your objects behave like built-ins.
11. **[Iterators & Generators](11-iterators-and-generators.md)** 🟡 - `yield`, laziness, processing huge data without the RAM.
12. **[Decorators](12-decorators.md)** 🔴 - the `@` magic in every framework, demystified.
13. **[Context Managers](13-context-managers.md)** 🟡 - `with`, and never leaking a file/lock/connection again.
14. **[Type Hints & mypy](14-type-hints.md)** 🟡 - gradual typing; catch the bug before runtime.
15. **[Dataclasses & Modern Modeling](15-dataclasses.md)** 🟡 - kill the boilerplate.
16. **[Concurrency & the GIL](16-concurrency-and-the-gil.md)** 🔴 - threads vs processes vs async, and what the GIL actually blocks.
17. **[Performance & Memory](17-performance-and-memory.md)** 🔴 - how CPython runs, the GC, and the real speedups.
18. **[Packaging & Environments](18-packaging-and-environments.md)** 🟡 - ship a package, not a folder of scripts.

**Finale**
19. **[Where to Go Next](19-where-to-go-next.md)** 🟢 - web, data, automation, and what to build.

> Frameworks (FastAPI, Django) are their own guides - they're different tools, not "more Python." This
> guide makes the *language* make sense, top to bottom.