[Tutor] Python GPIO Code Help Needed

Dave Angel davea at davea.name
Mon Oct 27 01:43:50 CET 2014


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Bill Bright <wcb_rlb at bellsouth.net> Wrote in message:
> 
> 
 The code below seems to work. My question is why does oldstates need to be multiplied by 32? Does this means the code will only read 32 switch changes? That would be a problem.

If you're just learning Python,  you need to actually play with
 each new concept you encounter. When you multiply a list by an
 int n, you create a new list, n times as big. Experiment with
 this in the interpreter,  till you understand. 

["A", "f", 42] *3
[] * 4000
[True, False] * 10

So you wind up with 32 flags in the oldstates list. Why 32? I
 don't have a rpi, so I took the wild guess that a Raspberry Pi
 might have 32 inputs. You're only using 3, so you could have used
 a list of 3, or a dict. But I was trying for the minimum
 complication. 

Others have mentioned an event loop in GPIO. Assuming such exists,
 it would be better to use it.
-- 
DaveA



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