Remove "connected" attribute (#402)

* Remove "connected" attribute

Fixes #327

* Fix things

* I'm terrible at both staging and committing everything

* Update error name and text

* Fix things

* Revert GyroBalancer changes

* Strip exception context when device isn't connected

Author: WasabiFan

ev3dev/__init__.py

@@ -124,13 +124,16 @@ def matches(attribute, pattern):
                 yield f
 
 
+class DeviceNotFound(Exception):
+    pass
+
 # -----------------------------------------------------------------------------
 # Define the base class from which all other ev3dev classes are defined.
 
 class Device(object):
     """The ev3dev device base class"""
 
-    __slots__ = ['_path', 'connected', '_device_index', 'kwargs']
+    __slots__ = ['_path', '_device_index', 'kwargs']
 
     DEVICE_ROOT_PATH = '/sys/class'
 
@@ -158,7 +161,7 @@ def __init__(self, class_name, name_pattern='*', name_exact=False, **kwargs):
             d = ev3dev.Device('tacho-motor', address='outA')
             s = ev3dev.Device('lego-sensor', driver_name=['lego-ev3-us', 'lego-nxt-us'])
 
-        When connected succesfully, the `connected` attribute is set to True.
+        If there was no valid connected device, an error is thrown.
         """
 
         classpath = abspath(Device.DEVICE_ROOT_PATH + '/' + class_name)
@@ -174,23 +177,24 @@ def get_index(file):
         if name_exact:
             self._path = classpath + '/' + name_pattern
             self._device_index = get_index(name_pattern)
-            self.connected = True
         else:
             try:
                 name = next(list_device_names(classpath, name_pattern, **kwargs))
                 self._path = classpath + '/' + name
                 self._device_index = get_index(name)
-                self.connected = True
             except StopIteration:
                 self._path = None
                 self._device_index = None
-                self.connected = False
+                raise DeviceNotFound("%s is not connected." % self) from None
 
     def __str__(self):
         if 'address' in self.kwargs:
             return "%s(%s)" % (self.__class__.__name__, self.kwargs.get('address'))
         else:
             return self.__class__.__name__
+    
+    def __repr__(self):
+        return self.__str__()
 
     def _attribute_file_open(self, name):
         path = os.path.join(self._path, name)
@@ -209,35 +213,27 @@ def _attribute_file_open(self, name):
 
     def _get_attribute(self, attribute, name):
         """Device attribute getter"""
-        if self.connected:
+        if attribute is None:
+            attribute = self._attribute_file_open( name )
+        else:
+            attribute.seek(0)
+        return attribute, attribute.read().strip().decode()
+
+    def _set_attribute(self, attribute, name, value):
+        """Device attribute setter"""
+        try:
             if attribute is None:
                 attribute = self._attribute_file_open( name )
             else:
                 attribute.seek(0)
-            return attribute, attribute.read().strip().decode()
-        else:
-            #log.info("%s: path %s, attribute %s" % (self, self._path, name))
-            raise Exception("%s is not connected" % self)
 
-    def _set_attribute(self, attribute, name, value):
-        """Device attribute setter"""
-        if self.connected:
-            try:
-                if attribute is None:
-                    attribute = self._attribute_file_open( name )
-                else:
-                    attribute.seek(0)
-
-                if isinstance(value, str):
-                    value = value.encode()
-                attribute.write(value)
-                attribute.flush()
-            except Exception as ex:
-                self._raise_friendly_access_error(ex, name)
-            return attribute
-        else:
-            #log.info("%s: path %s, attribute %s" % (self, self._path, name))
-            raise Exception("%s is not connected" % self)
+            if isinstance(value, str):
+                value = value.encode()
+            attribute.write(value)
+            attribute.flush()
+        except Exception as ex:
+            self._raise_friendly_access_error(ex, name)
+        return attribute
 
     def _raise_friendly_access_error(self, driver_error, attribute):
         if not isinstance(driver_error, OSError):
@@ -256,7 +252,7 @@ def _raise_friendly_access_error(self, driver_error, attribute):
             # We will assume that a file-not-found error is the result of a disconnected device
             # rather than a library error. If that isn't the case, at a minimum the underlying
             # error info will be printed for debugging.
-            raise Exception("%s is no longer connected" % self) from driver_error
+            raise DeviceNotFound("%s is no longer connected" % self) from driver_error
         raise driver_error
 
     def get_attr_int(self, attribute, name):

tests/api_tests.py

@@ -21,25 +21,20 @@ def test_device(self):
         populate_arena({'medium_motor' : [0, 'outA'], 'infrared_sensor' : [0, 'in1']})
 
         d = ev3.Device('tacho-motor', 'motor*')
-        self.assertTrue(d.connected)
 
         d = ev3.Device('tacho-motor', 'motor0')
-        self.assertTrue(d.connected)
 
         d = ev3.Device('tacho-motor', 'motor*', driver_name='lego-ev3-m-motor')
-        self.assertTrue(d.connected)
 
         d = ev3.Device('tacho-motor', 'motor*', address='outA')
-        self.assertTrue(d.connected)
 
-        d = ev3.Device('tacho-motor', 'motor*', address='outA', driver_name='not-valid')
-        self.assertTrue(not d.connected)
+        with self.assertRaises(ev3.DeviceNotFound):
+            d = ev3.Device('tacho-motor', 'motor*', address='outA', driver_name='not-valid')
 
         d = ev3.Device('lego-sensor', 'sensor*')
-        self.assertTrue(d.connected)
 
-        d = ev3.Device('this-does-not-exist')
-        self.assertFalse(d.connected)
+        with self.assertRaises(ev3.DeviceNotFound):
+            d = ev3.Device('this-does-not-exist')
 
     def test_medium_motor(self):
         def dummy(self):
@@ -53,8 +48,6 @@ def dummy(self):
 
         m = MediumMotor()
 
-        self.assertTrue(m.connected);
-
         self.assertEqual(m.device_index, 0)
 
         # Check that reading twice works:
@@ -86,8 +79,6 @@ def test_infrared_sensor(self):
 
         s = InfraredSensor()
 
-        self.assertTrue(s.connected)
-
         self.assertEqual(s.device_index,    0)
         self.assertEqual(s.bin_data_format, 's8')
         self.assertEqual(s.bin_data('<b'),  (16,))

utils/move_motor.py

@@ -33,10 +33,6 @@
 else:
     raise Exception("%s is invalid, options are A, B, C, D")
 
-if not motor.connected:
-    log.error("%s is not connected" % motor)
-    sys.exit(1)
-
 if args.degrees:
     log.info("Motor %s, current position %d, move to position %d, max speed %d" %
              (args.motor, motor.position, args.degrees, motor.max_speed))