Files on This Port

A microcontroller's files live on a small flash filesystem. The unix port instead shows MicroPython the machine's real filesystem — same files your other programs see. That makes this port the easy place to learn the file half of the language, and this chapter is exactly that, with one excursion that marks the boundary of the port.

Writing, reading, listing, and tidying up, in a scratch directory:

$ micropython -c "import os; print(os.getcwd())"
/home/hatch/workspace/micropython-lab/work

$ micropython -c "print(open("log.txt").read())"
Mon 21.5
Tue 23.0

$ micropython -c "import os; print(sorted(os.listdir("."))); print(os.stat("log.txt"))"
['log.txt']
(33184, 7615074, 86, 1, 0, 65534, 18, 1792551175, 1792551175, 1792551175)

(The write itself is in the same transcript: open in "w" mode, write two lines, close.) Everything here is ordinary: open with the usual modes, os.getcwd, os.listdir, os.remove. Two differences are worth naming. os.stat returns a plain tuple of ten integers — mode, inode, device, links, ids, size, and three timestamps — where CPython returns a named stat_result object you can also index like a tuple; code that reads .st_size by name needs the index ([6]) here. And the file is a real file: after the run it can be read by any other program, because on this port there is no "inside" and "outside" of MicroPython.

The machine module, present and empty-handed

Chapter 3's import test said machine imports on the unix port. So it does:

$ micropython -c "import machine; print([n for n in dir(machine) if not n.startswith("_")])"
['PinBase', 'Signal', 'idle', 'mem16', 'mem32', 'mem8', 'soft_reset', 'time_pulse_us']

Memory pokes (mem8/16/32), an idle, a Signal helper — the spillover of a shared codebase. But the name everyone reaches for first is not there:

$ micropython -c "import machine; p = machine.Pin(2, machine.Pin.OUT)"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'machine' has no attribute 'Pin'

There are no pins on a Linux process for Pin to drive, so the unix port does not pretend. That AttributeError is the exact border of this guide's lab: everything up to it runs, everything past it — pins, buses, timers, real interrupts — is board territory, and it is gathered, labelled, in chapter 11.

Check: micropython -c "import sys; print(sys.platform)" prints linux here. On a board the same line names the board's platform — the cheapest port detector a program can run before it reaches for hardware.