Create the EventLoop abstract class, add documentation for signal han…

…dling, use Python .gitignore provided by GitHub

.gitignore

@@ -1,16 +1,104 @@
-.DS_Store
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
 
-*.pyc
-*.pyo
+# C extensions
+*.so
 
-*.egg-info
-_build
-build
-dist
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
 MANIFEST
 
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
 .coverage
-coverage
-htmlcov
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+.hypothesis/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+.static_storage/
+.media/
+local_settings.py
+
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+instance/
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+.spyderproject
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+/site
 
-_trial_temp
+# mypy
+.mypy_cache/

urwid/main_loop.py

@@ -587,7 +587,103 @@ def draw_screen(self):
         self.screen.draw_screen(self.screen_size, canvas)
 
 
-class SelectEventLoop(object):
+class EventLoop(object):
+    """
+    Abstract class representing an event loop to be used by :class:`MainLoop`.
+    """
+
+    def alarm(self, seconds, callback):
+        """
+        Call callback() a given time from now.  No parameters are
+        passed to callback.
+
+        This method has no default implementation.
+
+        Returns a handle that may be passed to remove_alarm()
+
+        seconds -- floating point time to wait before calling callback
+        callback -- function to call from event loop
+        """
+        raise NotImplementedError()
+
+    def enter_idle(self, callback):
+        """
+        Add a callback for entering idle.
+
+        This method has no default implementation.
+
+        Returns a handle that may be passed to remove_idle()
+        """
+        raise NotImplementedError()
+
+    def remove_alarm(self, handle):
+        """
+        Remove an alarm.
+
+        This method has no default implementation.
+
+        Returns True if the alarm exists, False otherwise
+        """
+        raise NotImplementedError()
+
+    def remove_enter_idle(self, handle):
+        """
+        Remove an idle callback.
+
+        This method has no default implementation.
+
+        Returns True if the handle was removed.
+        """
+        raise NotImplementedError()
+
+    def remove_watch_file(self, handle):
+        """
+        Remove an input file.
+
+        This method has no default implementation.
+
+        Returns True if the input file exists, False otherwise
+        """
+        raise NotImplementedError()
+
+    def run(self):
+        """
+        Start the event loop.  Exit the loop when any callback raises
+        an exception.  If ExitMainLoop is raised, exit cleanly.
+
+        This method has no default implementation.
+        """
+        raise NotImplementedError()
+
+    def watch_file(self, fd, callback):
+        """
+        Call callback() when fd has some data to read.  No parameters
+        are passed to callback.
+
+        This method has no default implementation.
+
+        Returns a handle that may be passed to remove_watch_file()
+
+        fd -- file descriptor to watch for input
+        callback -- function to call when input is available
+        """
+        raise NotImplementedError()
+
+    def set_signal_handler(self, signum, handler):
+        """
+        Sets the signal handler for signal signum.
+
+        The default implementation of :meth:`set_signal_handler` 
+        is simply a proxy function that calls :func:`signal.signal()`
+        and returns the resulting value.
+
+        signum -- signal number
+        handler -- function (taking signum as its single argument),
+        or `signal.SIG_IGN`, or `signal.SIG_DFL`
+        """
+        return signal.signal(signum, handler)
+
+class SelectEventLoop(EventLoop):
     """
     Event loop based on :func:`select.select`
     """
@@ -651,12 +747,6 @@ def remove_watch_file(self, handle):
             return True
         return False
 
-    def set_signal_handler(self, signum, handler):
-        """
-        Proxy function to signal.signal()
-        """
-        return signal.signal(signum, handler)
-
     def enter_idle(self, callback):
         """
         Add a callback for entering idle.
@@ -736,7 +826,7 @@ def _loop(self):
             self._did_something = True
 
 
-class GLibEventLoop(object):
+class GLibEventLoop(EventLoop):
     """
     Event loop based on GLib.MainLoop
     """
@@ -775,9 +865,22 @@ def ret_false():
 
     def set_signal_handler(self, signum, handler):
         """
-        Sets a handler for a specified signal.  This method's behaviour
-        method tries to imitate the signal() function from the signal
-        module.
+        Sets the signal handler for signal signum.
+
+        .. WARNING::
+            Because this method uses the `GLib`-specific `unix_signal_add`
+            function, its behaviour is different than `signal.signal().`
+
+            If `signum` is not `SIGHUP`, `SIGINT`, `SIGTERM`, `SIGUSR1`,
+            `SIGUSR2` or `SIGWINCH`, this method performs no actions and
+            immediately returns None.
+
+            Returns None in all cases (unlike :func:`signal.signal()`).
+        ..
+
+        signum -- signal number
+        handler -- function (taking signum as its single argument),
+        or `signal.SIG_IGN`, or `signal.SIG_DFL`
         """
         glib_signals = [
             signal.SIGHUP,
@@ -924,7 +1027,7 @@ def wrapper(*args,**kargs):
         return wrapper
 
 
-class TornadoEventLoop(object):
+class TornadoEventLoop(EventLoop):
     """ This is an Urwid-specific event loop to plug into its MainLoop.
         It acts as an adaptor for Tornado's IOLoop which does all
         heavy lifting except idle-callbacks.
@@ -1034,12 +1137,6 @@ def remove_watch_file(self, handle):
             self._ioloop.remove_handler(fd)
             return True
 
-    def set_signal_handler(self, signum, handler):
-        """
-        Proxy function to signal.signal()
-        """
-        return signal.signal(signum, handler)
-
     def enter_idle(self, callback):
         self._max_idle_handle += 1
         handle   = self._max_idle_handle
@@ -1090,7 +1187,7 @@ def doRead(self):
         return self.cb()
 
 
-class TwistedEventLoop(object):
+class TwistedEventLoop(EventLoop):
     """
     Event loop based on Twisted_
     """
@@ -1185,12 +1282,6 @@ def remove_watch_file(self, handle):
             return True
         return False
 
-    def set_signal_handler(self, signum, handler):
-        """
-        Proxy function to signal.signal()
-        """
-        return signal.signal(signum, handler)
-
     def enter_idle(self, callback):
         """
         Add a callback for entering idle.
@@ -1276,7 +1367,7 @@ def wrapper(*args,**kargs):
         return wrapper
 
 
-class AsyncioEventLoop(object):
+class AsyncioEventLoop(EventLoop):
     """
     Event loop based on the standard library ``asyncio`` module.
 
@@ -1338,12 +1429,6 @@ def remove_watch_file(self, handle):
         """
         return self._loop.remove_reader(handle)
 
-    def set_signal_handler(self, signum, handler):
-        """
-        Proxy function to signal.signal()
-        """
-        return signal.signal(signum, handler)
-
     def enter_idle(self, callback):
         """
         Add a callback for entering idle.