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Level: 101 · for anyone starting from zero

One line: This library teaches Python one idea per page, and every claim on every page is backed by a stdlib-only program that runs in CI and is checked against its recorded output — so nothing here can quietly go stale.

What this is

A learning library about Python, built the same way as its siblings: one folder per idea, a page that makes a claim, and a program that proves it. The programs use nothing but the standard library, so you can run any page with the python3 already on your machine.

It starts with text and bytes rather than with syntax, for a specific reason. Most Python tutorials cover str in an afternoon and move on. But the text model is where a wrong mental picture survives longest before failing — and when it fails, it fails on someone else's data, in production, in a country whose alphabet you didn't test with. It is also the part of Python that differs most from C, ABAP and Rust, so it is where cross-referencing the other libraries pays.

Can you do these four things?

A diagnostic, not a test. Each one is a checkpoint, and each has a page.

  1. Say what len() counts, and name a case where two "obviously equal" strings compare False. → Counting characters
  2. Explain which of .encode() and .decode() you can call on a str, without guessing. → Encode and decode
  3. Say what encoding open("data.txt") uses on your machine, and on a colleague's. → Opening a file
  4. Sort a list of Polish names correctly, and say what you traded to do it. → Sorting is not comparing

If all four are comfortable, chapter 1 is revision — skim the crosswalk instead and start at chapter 2, which is about everything around the code rather than in it: the project file, the interpreter, and the packages it can see.

How to run anything here

Every example is a plain file with no dependencies:

python3 01_Text_and_Bytes/sorting_is_not_comparing/examples/sorting_is_not_comparing_py.py

To check that every page still matches what its program prints — which is what CI does on both Ubuntu and macOS:

python3 tools/run_examples.py --check

The reading order

  1. Text and bytes — the whole of chapter 1
  2. Projects and environments — the project file, and the interpreter that runs it
  3. The crosswalk — the same ideas in Rust, C and ABAP
  4. Roadmap — what is written, what is a stub, and what is next