On Tue, 20 Feb 2018 00:22:32 -0500
Dennis Lee Bieber  wrote:

> On Mon, 19 Feb 2018 19:08:31 -0800 (PST), ewholz@gmail.com declaimed the
> following:
>
>
> >I leave the program running, and detect when door opens, and when door
> >closes - but desire just one line of "OPEN" or "CLOSE"
> >
>
>  Without providing any actual code...
>
>  You need to keep a "history" state... AND you need to use an
> IF/ELSE-IF structure.
>
>  newState = readPin()
>  if lastState == closed and newState == opened:
>   print opened
>  elif lastState == opened and newState == closed:
>   print closed
>  lastState = newState
>
>  Using two IF blocks, without an ELSE block means the second IF
> gets tested even after you execute the contents of the first IF -- and
> the first IF (in your code) has set the history such that the other IF
> triggers and outputs...

 Actually the way you have it written the state is not set until
after both ifs so you could use an if instead of an elif (but the elif is
more efficient FWIW) - an alternative construction that makes it really
obvious that the trigger for printing is a state change goes like this:

 newState = readPin()
 if lastState != newState:
  if newState == opened:
   print "Opened"
  else:
   print "Closed"
 newState = lastState

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