On Tuesday, February 20, 2018 at 10:30:05 AM UTC-8, Ahem A Rivet's Shot wrote:
> 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
>
> --
> Steve O'Hara-Smith                          |   Directable Mirror Arrays
> C:\>WIN                                     | A better way to focus the sun
> The computer obeys and wins.                |    licences available see
> You lose and Bill collects.                 |    http://www.sohara.org/

Another good suggestion - i did not expect so many replies! Thanks

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