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110 lines
4.1 KiB
Python
110 lines
4.1 KiB
Python
#!/usr/bin/env python
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#
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# A library that provides a Python interface to the Telegram Bot API
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# Copyright (C) 2015-2020
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# Leandro Toledo de Souza <devs@python-telegram-bot.org>
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser Public License for more details.
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#
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# You should have received a copy of the GNU Lesser Public License
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# along with this program. If not, see [http://www.gnu.org/licenses/].
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"""This module contains the Promise class."""
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import logging
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from threading import Event
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from telegram.utils.types import JSONDict, HandlerArg
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from typing import Callable, List, Tuple, Optional, Union, TypeVar
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RT = TypeVar('RT')
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logger = logging.getLogger(__name__)
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class Promise:
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"""A simple Promise implementation for use with the run_async decorator, DelayQueue etc.
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Args:
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pooled_function (:obj:`callable`): The callable that will be called concurrently.
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args (:obj:`list` | :obj:`tuple`): Positional arguments for :attr:`pooled_function`.
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kwargs (:obj:`dict`): Keyword arguments for :attr:`pooled_function`.
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update (:class:`telegram.Update`, optional): The update this promise is associated with.
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error_handling (:obj:`bool`, optional): Whether exceptions raised by :attr:`func`
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may be handled by error handlers. Defaults to :obj:`True`.
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Attributes:
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pooled_function (:obj:`callable`): The callable that will be called concurrently.
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args (:obj:`list` | :obj:`tuple`): Positional arguments for :attr:`pooled_function`.
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kwargs (:obj:`dict`): Keyword arguments for :attr:`pooled_function`.
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done (:obj:`threading.Event`): Is set when the result is available.
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update (:class:`telegram.Update`): Optional. The update this promise is associated with.
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error_handling (:obj:`bool`): Optional. Whether exceptions raised by :attr:`func`
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may be handled by error handlers. Defaults to :obj:`True`.
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"""
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# TODO: Remove error_handling parameter once we drop the @run_async decorator
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def __init__(
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self,
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pooled_function: Callable[..., RT],
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args: Union[List, Tuple],
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kwargs: JSONDict,
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update: HandlerArg = None,
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error_handling: bool = True,
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):
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self.pooled_function = pooled_function
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self.args = args
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self.kwargs = kwargs
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self.update = update
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self.error_handling = error_handling
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self.done = Event()
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self._result: Optional[RT] = None
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self._exception: Optional[Exception] = None
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def run(self) -> None:
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"""Calls the :attr:`pooled_function` callable."""
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try:
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self._result = self.pooled_function(*self.args, **self.kwargs)
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except Exception as exc:
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self._exception = exc
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finally:
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self.done.set()
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def __call__(self) -> None:
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self.run()
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def result(self, timeout: float = None) -> Optional[RT]:
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"""Return the result of the ``Promise``.
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Args:
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timeout (:obj:`float`, optional): Maximum time in seconds to wait for the result to be
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calculated. ``None`` means indefinite. Default is ``None``.
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Returns:
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Returns the return value of :attr:`pooled_function` or ``None`` if the ``timeout``
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expires.
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Raises:
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Any exception raised by :attr:`pooled_function`.
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"""
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self.done.wait(timeout=timeout)
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if self._exception is not None:
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raise self._exception # pylint: disable=raising-bad-type
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return self._result
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@property
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def exception(self) -> Optional[Exception]:
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"""The exception raised by :attr:`pooled_function` or ``None`` if no exception has been
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raised (yet)."""
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return self._exception
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