Source code for watchdog.observers

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2011 Yesudeep Mangalapilly <yesudeep@gmail.com>
# Copyright 2012 Google, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
:module: watchdog.observers
:synopsis: Observer that picks a native implementation if available.
:author: yesudeep@google.com (Yesudeep Mangalapilly)


Classes
=======
.. autoclass:: Observer
   :members:
   :show-inheritance:
   :inherited-members:

You can also import platform specific classes directly and use it instead
of :class:`Observer`.  Here is a list of implemented observer classes.:

============== ================================ ==============================
Class          Platforms                        Note
============== ================================ ==============================
|Inotify|      Linux 2.6.13+                    ``inotify(7)`` based observer
|FSEvents|     Mac OS X                         FSEvents based observer
|Kqueue|       Mac OS X and BSD with kqueue(2)  ``kqueue(2)`` based observer
|WinApi|       MS Windows                       Windows API-based observer
|Polling|      Any                              fallback implementation
============== ================================ ==============================

.. |Inotify|     replace:: :class:`.inotify.InotifyObserver`
.. |FSEvents|    replace:: :class:`.fsevents.FSEventsObserver`
.. |Kqueue|      replace:: :class:`.kqueue.KqueueObserver`
.. |WinApi|      replace:: :class:`.read_directory_changes.WindowsApiObserver`
.. |WinApiAsync| replace:: :class:`.read_directory_changes_async.WindowsApiAsyncObserver`
.. |Polling|     replace:: :class:`.polling.PollingObserver`

"""

from watchdog.utils.importlib2 import import_module

OBS_PROVIDERS = (
    ('inotify', 'InotifyObserver'),
    ('fsevents', 'FSEventsObserver'),
    ('kqueue', 'KqueueObserver'),
    ('read_directory_changes_async', 'WindowsApiAsyncObserver'),
    ('read_directory_changes', 'WindowsApiObserver'),
    ('polling', 'PollingObserver')
)


def _lookup_obs():
    c = None
    for mod, cls in OBS_PROVIDERS:
        m_name = 'watchdog.observers.%s' % mod
        try:
            c = import_module(cls, m_name)
        except (ImportError, AttributeError):  # more exceptions?
            continue
        return c

Observer = _lookup_obs()

"""
Observer thread that schedules watching directories and dispatches
calls to event handlers.
"""