Don't error if device switched off

Previously get_device or the related functions would retrieve a list of
devices that it contacted in the last x seconds. Then we would contact
each light in turn to try and apply some sort of filtering.

This would error out if the light had been switched off.

This patch attempts to contact each light and skips it if it cannot be
contacted.

Closes smarthall#6

lifx/client.py

@@ -169,11 +169,12 @@ def poll_devices(self):
         for device in filter(lambda x:x.seen_ago > poll_delta,  self._devices.values()):
             device.send_poll_packet()
 
-    def get_devices(self, max_seen=None):
+    def get_devices(self, max_seen=None, filter=None):
         """
         Get a list of all responding devices.
 
         :param max_seen: The number of seconds since the device was last seen, defaults to 3 times the devicepoll interval.
+        :param filter: Filter list of devices using this function
         """
         if max_seen is None:
             max_seen = self._devicepolltime * MISSED_POLLS
@@ -182,6 +183,19 @@ def get_devices(self, max_seen=None):
 
         devices = filter(lambda x:x.seen_ago < seen_delta, self._devices.values())
 
+        alive = []
+        for d in devices:
+            try:
+                if filter is not None:
+                    if filter(d):
+                        alive.append(d)
+                else:
+                    d.latency
+                    alive.append(d)
+            except device.DeviceTimeoutError:
+                pass
+        devices = alive
+
         # Sort by device id to ensure consistent ordering
         return sorted(devices, key=lambda k:k.id)
 
@@ -227,7 +241,7 @@ def by_label(self, label):
         :param by_label: The label we are looking for.
         :returns: list -- The devices that match criteria
         """
-        return filter(lambda d: d.label == label, self.get_devices())
+        return self.get_devices(filter=lambda d: d.label == label)
 
     def by_id(self, id):
         """
@@ -236,7 +250,7 @@ def by_id(self, id):
         :param id: The device id
         :returns: Device -- The device with the matching id.
         """
-        return filter(lambda d: d.id == id, self.get_devices())[0]
+        return self.get_devices(filter=lambda d: d.id == id)
 
     def by_power(self, power):
         """
@@ -245,7 +259,7 @@ def by_power(self, power):
         :param power: True returns all devices that are on, False returns ones that are off.
         :returns: list -- The devices that match criteria
         """
-        return filter(lambda d: d.power == power, self.get_devices())
+        return self.get_devices(filter=lambda d: d.power == power)
 
     def by_group_id(self, group_id):
         """
@@ -254,7 +268,7 @@ def by_group_id(self, group_id):
         :param group_id: The group id to match on each light.
         :returns: list -- The devices that match criteria
         """
-        return filter(lambda d: d.group_id == group_id, self.get_devices())
+        return self.get_devices(filter=lambda d: d.group_id == group_id)
 
     def by_location_id(self, location_id):
         """
@@ -263,7 +277,7 @@ def by_location_id(self, location_id):
         :param group_id: The group id to match on each light.
         :returns: list -- The devices that match criteria
         """
-        return filter(lambda d: d.location_id == location_id, self.get_devices())
+        return self.get_devices(filter=lambda d: d.location_id == location_id)
 
     def __getitem__(self, key):
         return self.get_devices()[key]