using tsl.lux can produce unanticipated Exception

[csylvain]

using tsl.lux without consideration of all possible values will eventually produce an unanticipated Exception.
return values can be a float, 0, or None.
implicit datatype handling provides float(0) == 0.0 but float(None) will produce an Exception.
alternatively, one should check isinstance( tsl.lux, Float ) but that would not explicitly show tsl.lux can be None in this example.

[tannewt]

Thanks for the clarification. One more question about it.

[caternuson]

If we change this:
https://github.com/adafruit/Adafruit_CircuitPython_TSL2561/blob/master/adafruit_tsl2561.py#L180
to

lux = 0.

Then returns would either be a float or None. Checking would still need to be done for None, but that is a general issue with any sensor that may return None to indicate a bad reading. For example, this could also potentially throw an unexpected exception:

if tsl.lux > SOME_THRESHOLD:
    print("bright light! bright light!")

when trying to do a comparison with None.

In general, the simpletest examples assume goodness so the code can be brief. Adding that conditional check isn't too much though, if you think having it would help. Instead of saying it's a NaN or None, could also say something like "bad sensor reading" in the print.

@tannewt What would be the additional info? Are you thinking just docstring or something in actual code?

[csylvain]

i encountered this issue because of using %0.1f to format the value of lux. 'as built', python is very forgiving about 0.0 versus 0 but if you want to be very lint-y then, yes, it ought to be 0.0 to skip the implicit datatype conversion in code using this module.

[csylvain]

the Exception due to None being returned was a surprise (to me) since the docs didn't say anything about the lux method not returning a float when taking readings using the default gain and integration time while logging the diurnal cycle at a rural north-facing window. dark sky abounds here at night.

[tannewt]

@caternuson I meant in the property docstring. More details in the threaded conversation.

[caternuson]

@tannewt Thanks. That's my bad, so I will fix.

@csylvain I will follow your PR with one of my own to update the docstrings and insure a float return.

[tannewt]

Thanks @csylvain and @caternuson