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import asyncio
import contextvars
import functools
# Used as an alternative for asyncio.to_thread in python <=3.8
# Repurposed from CPython, used under the terms of the PSL
# Upstream source: https://github.com/python/cpython/blob/4b4227b907a262446b9d276c274feda2590a4e6e/Lib/asyncio/threads.py
# License: https://github.com/python/cpython/blob/4b4227b907a262446b9d276c274feda2590a4e6e/LICENSE
# Copyright (c) 2021 Python Software Foundation
async def _to_thread(func, *args, **kwargs):
"""Asynchronously run function *func* in a separate thread.
Any *args and **kwargs supplied for this function are directly passed
to *func*. Also, the current :class:`contextvars.Context` is propagated,
allowing context variables from the main thread to be accessed in the
separate thread.
Return a coroutine that can be awaited to get the eventual result of *func*.
"""
loop = asyncio.get_running_loop()
ctx = contextvars.copy_context()
func_call = functools.partial(ctx.run, func, *args, **kwargs)
return await loop.run_in_executor(None, func_call)
to_thread = getattr(asyncio, 'to_thread', _to_thread)
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