Lazily evaluate conditions

[CamDavidsonPilon]

I am writing some unit tests for my package that uses this library, and I take advantage of the BLINKA_FORCECHIP and BLINKA_FORCEBOARD environment variables to "mock" a board. However, my recent builds start failing with an error thrown in this library. Try to debug what might be going wrong, I came across a problem in the following LOC:

https://github.com/adafruit/Adafruit_Python_PlatformDetect/blob/main/adafruit_platformdetect/board.py#L619-L624

What was happening was that while any_raspberry_pi_40_pin would evaluate to True, any_raspberry_pi would thow an error (internally, it's looking for a specific file, which doesn't exist in my testing environment). I was actually surprised, since I know that any is lazy: it will prematurely exist once it finds the first True - however, the way the code is currently written, Python first creates the list [any_raspberry_pi_40_pin, any_raspberry_pi, ..., any_maaxboard], and then calls any on it. This means:

1. an error thrown in any of the any_ properties will be raised immediately (what I was observing),
2. we evaluate every condition, even if those conditions aren't checked. This has a performance cost. Most any_ are just lookups, but some, like any_raspberry_pi, involve an IO operation. Some quick tests suggest ~10% improvement in time taken.

Here's a simplified version of 1)

class Klass():
    @property
    def any_embedded_linux(self):
        return any([
            self.okay_prop,
            self.other_prop,
            self.bad_prop,
        ])

    @property
    def okay_prop(self):
        return True

    @property 
    def bad_prop(self):
        raise ValueError

    @property 
    def other_prop(self):
        return False

k = Klass()
print(k.any_embedded_linux)

and 2)

class Klass():

    @property
    def any_embedded_linux(self):
        return any([
            self.okay_prop,
            self.other_prop,
            self.sleepy_prop,
        ])

    @property
    def okay_prop(self):
        return True

    @property 
    def other_prop(self):
        return False

    @property
    def sleepy_prop(self):
        import time
        time.sleep(10)

k = Klass()
print(k.any_embedded_linux)

Anyways, a solution is to turn the list into a generator. This solves 1) and 2), but has a bit of a code smell to it (it's not obvious why we are doing this at first look, only after this explanation is provided).

Let me know your thoughts!

[CamDavidsonPilon]

an alternative way to do this is something like:

for prop in ["any_raspberry_pi_40_pin", "any_raspberry_pi", ...]:
      yield getattr(self, prop)

[makermelissa]

Sorry for the delay. I just merged new updates since you had submitted this and fixed any errors as a result of that since that was my fault.

[makermelissa]

Thanks for submitting this. I hope it helps performance.