Adds a loop property to SerialTransport.

Retrieve the event loop from the transport rather than relying on the vagaries of get_event_loop().
Tidies up the tests and example code to make it a bit clearer when the transport is set on the
protocol and to avoid linting issues.  Demonstrate how to retrieve the event loop from the
transport in the documentation.

Author: rob-smallshire

documentation/shortintro.rst

@@ -1,6 +1,6 @@
-====================
- Short introduction
-====================
+==================
+Short introduction
+==================
 
 Example::
 
@@ -18,7 +18,7 @@ Example::
 
         def connection_lost(self, exc):
             print('port closed')
-            asyncio.get_event_loop().stop()
+            self.transport.loop.stop()
 
         def pause_writing(self):
             print('pause writing')
@@ -33,3 +33,4 @@ Example::
     loop.run_until_complete(coro)
     loop.run_forever()
     loop.close()
+

serial_asyncio/__init__.py

@@ -67,13 +67,18 @@ def __init__(self, loop, protocol, serial_instance):
         loop.call_soon(protocol.connection_made, self)
         loop.call_soon(self._ensure_reader)
 
+    @property
+    def loop(self):
+        """The asyncio event loop used by this SerialTransport."""
+        return self._loop
+
     @property
     def serial(self):
         """The underlying Serial instance."""
         return self._serial
 
     def __repr__(self):
-        return '{self.__class__.__name__}({self._loop}, {self._protocol}, {self.serial})'.format(self=self)
+        return '{self.__class__.__name__}({self.loop}, {self._protocol}, {self.serial})'.format(self=self)
 
     def is_closing(self):
         """Return True if the transport is closing or closed."""
@@ -446,27 +451,32 @@ def open_serial_connection(*,
 # test
 if __name__ == '__main__':
     class Output(asyncio.Protocol):
+
+        def __init__(self):
+            super().__init__()
+            self._transport = None
+
         def connection_made(self, transport):
-            self.transport = transport
-            print('port opened', transport)
-            transport.serial.rts = False
-            transport.write(b'hello world\n')
+            self._transport = transport
+            print('port opened', self._transport)
+            self._transport.serial.rts = False
+            self._transport.write(b'Hello, World!\n')
 
         def data_received(self, data):
             print('data received', repr(data))
             if b'\n' in data:
-                self.transport.close()
+                self._transport.close()
 
         def connection_lost(self, exc):
             print('port closed')
-            asyncio.get_event_loop().stop()
+            self._transport.loop.stop()
 
         def pause_writing(self):
             print('pause writing')
-            print(self.transport.get_write_buffer_size())
+            print(self._transport.get_write_buffer_size())
 
         def resume_writing(self):
-            print(self.transport.get_write_buffer_size())
+            print(self._transport.get_write_buffer_size())
             print('resume writing')
 
     loop = asyncio.get_event_loop()

test/test_asyncio.py

@@ -40,39 +40,49 @@ def tearDown(self):
         self.loop.close()
 
     def test_asyncio(self):
-        TEXT = b'hello world\n'
+        TEXT = b'Hello, World!\n'
         received = []
         actions = []
 
         class Input(asyncio.Protocol):
+
+            def __init__(self):
+                super().__init__()
+                self._transport = None
+
             def connection_made(self, transport):
-                self.transport = transport
+                self._transport = transport
 
             def data_received(self, data):
-                self.transport.write(data)
+                self._transport.write(data)
 
         class Output(asyncio.Protocol):
+
+            def __init__(self):
+                super().__init__()
+                self._transport = None
+
             def connection_made(self, transport):
-                self.transport = transport
+                self._transport = transport
                 actions.append('open')
                 transport.write(TEXT)
 
             def data_received(self, data):
                 received.append(data)
                 if b'\n' in data:
-                    self.transport.close()
+                    self._transport.close()
 
             def connection_lost(self, exc):
                 actions.append('close')
-                asyncio.get_event_loop().stop()
+                self._transport.loop.stop()
 
             def pause_writing(self):
                 actions.append('pause')
-                print(self.transport.get_write_buffer_size())
+                print(self._transport.get_write_buffer_size())
 
             def resume_writing(self):
                 actions.append('resume')
-                print(self.transport.get_write_buffer_size())
+                print(self._transport.get_write_buffer_size())
 
         if PORT.startswith('socket://'):
             coro = self.loop.create_server(Input, HOST, _PORT)