only change lastchange timestamp if the state has changed

lastState.txt

@@ -0,0 +1 @@
+0 1470352249

state.py

@@ -7,6 +7,7 @@ import logging
 
 fileName = "json"
 url = "http://status.krautspace.de/status/button/"
+laststateFile = 'lastState.txt'
 
 data = None
 # Raum Status abrufen
@@ -15,7 +16,7 @@ try:
 except:
 	logging.exception("urllib2")
 else:
-	# Status lessen 
+	# Status lesen
 	data = response.read(1)
 	# Data validieren
 	if len(data) != 1 or data not in ("0", "1"):
@@ -33,19 +34,40 @@ except:
 
 # Bereich in dem der Status steht
 state = raw["state"]
-# letzte Verarbeitungszeit setzen
-state["lastchange"] = int(time.time())
+
+try:
+	fp = file(laststateFile)
+	lastState, oldTimestamp = fp.readline().split()
+	fp.close()
+except:
+	logging.exception("file")
+	exit(1)
+
 # Status setzen
 if data:
-	if data == "0":
-		state["open"] = False
-		state["message"] = "no human being on location"
+	if lastState != data:
+		currentTimestamp = int(time.time())
+		if data == "0":
+			state["lastchange"] = currentTimestamp
+			state["open"] = False
+			state["message"] = "no human being on location"
+		else:
+			state["lastchange"] = currentTimestamp
+			state["open"] = True
+			state["message"] = "open for public"
+		try:
+			fp = open( laststateFile, 'w' )
+			fp.write(data + ' ' + str(currentTimestamp))
+			fp.close()
+		except:
+			logging.exception("file")
+			exit(1)
 	else:
-		state["open"] = True
-		state["message"] = "open for public"
+		state["lastchange"] = oldTimestamp
 else:
 	state["open"] = None
 	state["message"] = "open for public"
+	state["lastchange"] = oldTimestamp
 
 # JSON Decodieren und ausgeben
 print json.dumps(raw)