Micropython and typing

[brianreinhold]

I really dislike the run time typing used by Python, Micropython, and Typescript (and perhaps other languages). When a project becomes large and creates objects with complex fields and structures and has to be understood by someone else, it becomes a nightmare. I don't want to put anyone else through that agony so I strictly type my code.

However, I have run into situations where it appears the typing causes a run time syntax error. For example, this line of code declaring a bunch of variables
conn_handle, start_handle, end_handle, uuid = data
runs fine on the PICO-W. But if I type it
conn_handle: int, start_handle: int, end_handle: int, uuid = data

it gives a syntax error.

Why?

[andrewleech]

Careful, you risk starting a flame war with those kind of statements ;-)
https://erik-engheim.medium.com/the-many-advantages-of-dynamic-languages-267d08f4c7

Splitting a tuple/list/etc out into separate variables is called "unpacking". Type hinting unpacking this way doesn't work in python either, it needs to be declared in a different way. A few suggestions have been made here: https://stackoverflow.com/questions/52082939/type-hints-when-unpacking-a-tuple

[Josverl]

you can also type the complex object, most static typecheckers will be able to follow that though into the variables that it is assigned to:
(and you can use that as a returned type on any methods you define in python, or in a .pyi stub file for any C-Module.

Code sample in pyright playground

from typing import Tuple, Union, reveal_type

FourTuple  =  Tuple[int, int, int, Union[int,str,bytes]]
data: FourTuple = (1, 2, 3, "4567")

conn_handle, start_handle, end_handle, uuid = data 

reveal_type(conn_handle)
reveal_type(end_handle)
reveal_type(uuid)

[GitHubsSilverBullet]

Instead of extensive typing, maybe the assert approach would be useful.

a =  [1,2,3,4,4.5]
for x in a:
    assert type(x) is int, f'{x} is not int'

AssertionError: 4.5 is not int

[Josverl]

Note: asserts are generally dropped when cross-compiling with -o2, which is common to optimize for speed&memory.

[Josverl]

FYI The Python typing community hangs out on : https://github.com/python/typing/discussions.
They have been helpful but may have complex answers to seemingly simple questions.

If you have a more elaborate example that you want some eyes on, feel free to tag me or post a snippet in a Gist

[brianreinhold]

@GitHubsSilverBullet I am primarily interested in typing to help others (and myself down the road) understand what my code is doing. It deals with Bluetooth which requires not only understanding of what I am trying to do but the Bluetooth spec. When all the variables are typed intellisense becomes a very helpful tool and is a great aid in not only writing code but understanding it.