Create arc.py Example for arc users (#9)

* Create arc.py

* Code review comments

* Fix other vairable

* PEP8

* Fix print formatting

Co-authored-by: Artem Popov <artfwo@gmail.com>

* Code review

* Use ring_range

Co-authored-by: Artem Popov <artfwo@gmail.com>

Co-authored-by: Artem Popov <artfwo@gmail.com>

examples/arc.py

@@ -0,0 +1,57 @@
+#! /usr/bin/env python3
+#
+# Test for a push-button monome arc
+
+import asyncio
+import monome
+
+
+class ExampleArcApp(monome.ArcApp):
+    def __init__(self):
+        super().__init__()
+        self.pos = [0, 0, 0, 0]
+
+    def on_arc_ready(self):
+        print('Ready, clearing all rings...')
+        for n in range(0, 4):
+            self.arc.ring_all(n, 0)
+
+    def on_arc_disconnect(self):
+        print('Arc disconnected.')
+
+    def on_arc_delta(self, ring, delta):
+        print(f'Ring: {ring} Delta: {delta}')
+
+        old_pos = self.pos[ring]
+        new_pos = old_pos + delta
+
+        if new_pos > old_pos:
+            self.arc.ring_range(ring, old_pos, new_pos, 15)
+        else:
+            self.arc.ring_range(ring, new_pos, old_pos, 5)
+
+        self.pos[ring] = new_pos
+
+    def on_arc_key(self, ring, s):
+        print(f'Ring: {ring} Pressed: {s > 0}')
+        self.arc.ring_all(ring, 15 if s > 0 else 0)
+
+
+if __name__ == '__main__':
+    loop = asyncio.get_event_loop()
+    app = ExampleArcApp()
+
+    def serialosc_device_added(id, type, port):
+        if 'arc' not in type:
+            print(f'ignoring {id} ({type}) as device does not appear to be an arc')
+            return
+
+        print(f'connecting to {id} ({type})')
+        asyncio.ensure_future(app.arc.connect('127.0.0.1', port))
+
+    serialosc = monome.SerialOsc()
+    serialosc.device_added_event.add_handler(serialosc_device_added)
+
+    loop.run_until_complete(serialosc.connect())
+
+    loop.run_forever()