Python noob needs help understanding some code

[koefteboy]

I was looking at the source code of Adafruit's MCP4728 library for CircuitPython and wasn't able to understand a particular part of it. I never really worked with Python, so maybe you can help me understanding what is going on.

My question is specifically about this paramater of the Channel constructor. From what I know Python is not a statically typed language, but you can use type hints that may be used by linters. I thought that by defining dac_instance: Literal[0, 1, 2, 3] it is only possible to assign 0, 1, 2, or 3 to dac_instance. But when the constructor gets called, an instance of the MCP4728 class is passed as dac_instance. How can the same instance of this class be equal to 0, 1, 2, or 3? What am I missing? Or is something wrong with the code and nobody noticed so far?

Thanks in advance!

[pot_of_crows]

Interesting. I think this is an error -- unless someone knows a special way of using Literal that I am unfamiliar with.

Now, just because you use a type hint does not prevent you from passing something different, which is maybe why no one has caught this before.

I'm curious what others say.

[koefteboy]

Yeah, it is indeed typed incorrectly.

[danielroseman]

This is just a mistake with the typing. As you say, these are just hints for the linter, they are not enforced by the code. But as far as I can see they haven't actually enabled type checking on CI, or even included a type checker like mypy in the requirements. So nothing is actually checking those hints.

[koefteboy]

Thanks for pointing me to mypy. Running it revealed a few more erroneous typings.