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promise.py
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92 lines (73 loc) · 3.18 KB
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#!/usr/bin/env python
#
# A library that provides a Python interface to the Telegram Bot API
# Copyright (C) 2015-2018
# Leandro Toledo de Souza <devs@python-telegram-bot.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser Public License for more details.
#
# You should have received a copy of the GNU Lesser Public License
# along with this program. If not, see [http://www.gnu.org/licenses/].
"""This module contains the Promise class."""
import logging
from threading import Event
logger = logging.getLogger(__name__)
logger.addHandler(logging.NullHandler())
class Promise(object):
"""A simple Promise implementation for use with the run_async decorator, DelayQueue etc.
Args:
pooled_function (:obj:`callable`): The callable that will be called concurrently.
args (:obj:`list` | :obj:`tuple`): Positional arguments for :attr:`pooled_function`.
kwargs (:obj:`dict`): Keyword arguments for :attr:`pooled_function`.
Attributes:
pooled_function (:obj:`callable`): The callable that will be called concurrently.
args (:obj:`list` | :obj:`tuple`): Positional arguments for :attr:`pooled_function`.
kwargs (:obj:`dict`): Keyword arguments for :attr:`pooled_function`.
done (:obj:`threading.Event`): Is set when the result is available.
"""
def __init__(self, pooled_function, args, kwargs):
self.pooled_function = pooled_function
self.args = args
self.kwargs = kwargs
self.done = Event()
self._result = None
self._exception = None
def run(self):
"""Calls the :attr:`pooled_function` callable."""
try:
self._result = self.pooled_function(*self.args, **self.kwargs)
except Exception as exc:
logger.exception('An uncaught error was raised while running the promise')
self._exception = exc
finally:
self.done.set()
def __call__(self):
self.run()
def result(self, timeout=None):
"""Return the result of the ``Promise``.
Args:
timeout (:obj:`float`, optional): Maximum time in seconds to wait for the result to be
calculated. ``None`` means indefinite. Default is ``None``.
Returns:
Returns the return value of :attr:`pooled_function` or ``None`` if the ``timeout``
expires.
Raises:
Any exception raised by :attr:`pooled_function`.
"""
self.done.wait(timeout=timeout)
if self._exception is not None:
raise self._exception # pylint: disable=raising-bad-type
return self._result
@property
def exception(self):
"""The exception raised by :attr:`pooled_function` or ``None`` if no exception has been
raised (yet)."""
return self._exception