I have a tuple, RELAY_PINS that holds GPIO pin numbers in the order that the relays are installed. RELAY_PINS is immutable, and its ordering does not change, while the order that the devices are defined in changes frequently.
The MRE:
from random import shuffle, randint
class Device:
def __init__(self, pin_number):
self.pin_number = pin_number
def __str__(self):
return str(self.pin_number)
RELAY_PINS = ( 14, 15, 18, 23, 24, 25, 1, 12, 16, 20, 21, 26, 19, 13, 6, 5 )
def MRE():
devices = [ Device(pin) for pin in RELAY_PINS ]
# the ordering for the list of devices should be considered random for the sake of this question
shuffle(devices)
return devices
My solution “works”, but frankly, it’s embarrassing:
def main():
devices = MRE()
pin_map = { pin_number : index for index, pin_number in enumerate(RELAY_PINS) }
ordered_devices = [ None for _ in range(len(RELAY_PINS)) ]
for device in devices:
index = pin_map[device.pin_number]
ordered_devices[index] = device
return [ dev for dev in ordered_devices if dev is not None ]
I know there is a better solution, but I can’t quite wrap my head around it.
What is the pythonic solution to this problem?
3
You can use sorted with a key function:
from random import randint, shuffle
class Device:
def __init__(self, pin_number: int):
self.pin_number = pin_number
def __str__(self) -> str:
return str(self.pin_number)
def __repr__(self) -> str:
return f'Device(pin_number={self.pin_number})'
RELAY_PINS: tuple[int, ...] = (14, 15, 18, 23, 24, 25, 1, 12, 16, 20, 21, 26,
19, 13, 6, 5)
def MRE() -> None:
devices = [Device(pin) for pin in RELAY_PINS]
devices.pop(randint(0, len(RELAY_PINS) - 1))
shuffle(devices)
return devices
def main() -> None:
devices = MRE()
ordered_devices = sorted(devices, key=lambda d: RELAY_PINS.index(d.pin_number))
print(ordered_devices)
if __name__ == '__main__':
main()
Example Output (device with pin_number=12 randomly popped):
[Device(pin_number=14), Device(pin_number=15), Device(pin_number=18), Device(pin_number=23), Device(pin_number=24), Device(pin_number=25), Device(pin_number=1), Device(pin_number=16), Device(pin_number=20), Device(pin_number=21), Device(pin_number=26), Device(pin_number=19), Device(pin_number=13), Device(pin_number=6), Device(pin_number=5)]
4