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Date: Wed, 9 Apr 2014 08:34:26 -0500
From: Tim Chase <python.list@tim.thechases.com>
To: Grawburg <grawburg@myglnc.com>
Subject: Re: "Latching" variables in function
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References: <7ffe44a68f47a64f5120d3a6c6a660b5@myglnc.com>
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Xref: csiph.com comp.lang.python:69946

On 2014-04-08 16:09, Grawburg wrote:
> def button():
> =C2=A0 =C2=A0pushbutton =3D 0
> =C2=A0 button_value =3D 0
> =C2=A0 =C2=A0pushbutton=3Dbus.read_byte_data(address,GPIOB)
> =C2=A0 =C2=A0if pushbutton > 0:
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 button_value =3D 1
> =C2=A0 =C2=A0return button_value
>=20
> I need button_value to become '1' when the button is pressed and to
> remain '1' until the entire program (only about 25 lines) ends with
> a sys.exit()
>=20
> What do I use to 'latch' button_value?

If I understand what you want, you could do something like

  class LatchButton:
    def __init__(self, address):
      self.value =3D 0
      self.address =3D address
    def __call__(self):
      if not self.value:
        if bus.read_byte_data(self.address, GPIOB) > 0:
          self.value =3D 1
      return self.value

  button1 =3D LatchButton(address1)
  button2 =3D LatchButton(address2)
  for i in range(10):
    print button1(), button2()
    time.sleep(3)

-tkc