What MicroPython Is

MicroPython is an implementation of the Python 3 language, rewritten from scratch to fit where the ordinary Python — CPython, the one from python.org — cannot go: microcontrollers. A microcontroller is a whole small computer on one chip, with memory measured in kilobytes rather than gigabytes. MicroPython runs there, in a few hundred kilobytes, and still feels like Python: same syntax, same kinds of objects, same way of thinking.

The trade is scope, not spirit. To fit, MicroPython carries a subset of CPython's standard library, a smaller memory budget, and a language core that tracks an older Python's shape with selected newer features added. What exactly survives the squeeze is an empirical question — which is why this guide runs everything instead of asserting it.

One language, several ports

MicroPython is built per platform as a port: there is a port for the Raspberry Pi Pico's chip, several for ESP32 boards, one for the original pyboard, and — the one this guide uses — the unix port, which runs on Linux, macOS, and Windows like any other program. The unix port is the fullest build of MicroPython: it exists so people can develop and test on a desk machine, and it is more generous (more memory, more modules) than any chip build. Keep that generosity in mind; chapter 11 returns to it.

Ports come in variants (build flavours). This guide's binary reports its own:

$ micropython -c "import sys; print(sys.implementation); print(sys.version)"
(name='micropython', version=(1, 29, 0, ''), _machine='linux [GCC 13.3.0] version', _mpy=2822, _build='standard', _thread='unsafe')
3.4.0; MicroPython v1.29.0 on 2026-10-21

Read that output the way the guide will keep reading outputs: name is micropython, the version is 1.29.0, the build is standard, and sys.version claims 3.4.0 — MicroPython's language baseline is roughly Python 3.4's, with later features (you will meet f-strings and the walrus operator in this guide) adopted since. The referee, for comparison:

$ python3 -c "import sys; print(sys.implementation.name, sys.version.split()[0])"
cpython 3.12.3

The size of the thing

$ micropython --version
MicroPython v1.29.0 on 2026-10-21; linux [GCC 13.3.0] version

$ ls -lh bin/micropython
-rwxrwx--- 1 root nogroup 855K Oct 21 02:52 bin/micropython

The whole interpreter is one 855K file. That is the point of the project in a single number: a language small enough to live on a chip, here sitting on a Linux disk where you can take it apart. On a chip it is smaller still, but that build is documentation's word, not this lab's measurement.

Check: run the two commands above against any MicroPython you install. The banner names the version and the machine it was built for; if yours says something else, you have a different port or variant, and some details in this guide (mainly chapter 3's module list) will differ with it.

How this guide tests

Two interpreters, the same files. Fixtures live in examples/; the lab's transcripts (micropython-lab/transcripts/, t01–t13) hold the raw captures, and the chapters quote them. Where MicroPython and CPython agree, the guide says so and shows both outputs. Where they disagree — a missing module, a syntax error, a memory limit — the disagreement is the chapter. Hardware behaviour the unix port cannot exhibit is gathered in chapter 11 and labelled documented-only.