python 與 AsyncKernelManager 異步，Qt 未執行

Question

我正在嘗試在 Qt 應用程序中的 jupyter kernel 中執行代碼。 我有下面的代碼片段應該異步運行代碼然后打印結果

import sys
import asyncio

import qasync
from qasync import QApplication
from PySide6.QtWidgets import QWidget
from jupyter_client import AsyncKernelManager


CODE = """print('test')"""


class Test():
    def __init__(self):
        kernel_manager = AsyncKernelManager()
        kernel_manager.start_kernel()

        self.client = kernel_manager.client()
        self.client.start_channels()

    def run(self):
        loop = asyncio.get_event_loop()
        asyncio.ensure_future(self.execute(), loop=loop)

    async def execute(self):
        self.client.execute(CODE)
        response: Coroutine = self.client.get_shell_msg()
        print('Before')
        res = await response
        print('After')


def main():
    app = QApplication(sys.argv)
    test = Test()
    test.run()
    sys.exit(app.exec())


main()

通過以上我得到以下 output

/tmp/test/test.py:16: RuntimeWarning: coroutine 'KernelManager._async_start_kernel' was never awaited
  kernel_manager.start_kernel()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
/tmp/test/test.py:22: DeprecationWarning: There is no current event loop
  loop = asyncio.get_event_loop()

因此嘗試根據qasync中的示例將代碼調整為類似

async def main():
    app = QApplication(sys.argv)
    test = Test()
    test.run()
    sys.exit(app.exec())


qasync.run(main())

將導致以下異常

Traceback (most recent call last):
  File "/tmp/test/test.py", line 40, in <module>
    qasync.run(main())
  File "/tmp/test/.venv/lib/python3.10/site-packages/qasync/__init__.py", line 821, in run
    return asyncio.run(*args, **kwargs)
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/tmp/test/.venv/lib/python3.10/site-packages/qasync/__init__.py", line 409, in run_until_complete
    return future.result()
  File "/tmp/test/test.py", line 34, in main
    app = QApplication(sys.argv)
RuntimeError: Please destroy the QApplication singleton before creating a new QApplication instance.

在這一點上我很迷茫，有人知道如何讓它工作嗎？

Answer 1

你必須創建一個 QEventLoop，同時 start_kernel 必須使用 await。 另一方面，它首先導入 PySide6，然后導入依賴於 PySide6 的其他庫（如 qasync），以便它可以推斷出正確的 Qt 綁定。

import sys
import asyncio
from functools import cached_property

from PySide6.QtWidgets import QApplication
import qasync

from jupyter_client import AsyncKernelManager


CODE = """print('test')"""


class Test:
    @cached_property
    def kernel_manager(self):
        return AsyncKernelManager()

    @cached_property
    def client(self):
        return self.kernel_manager.client()

    async def start(self):
        await self.kernel_manager.start_kernel()
        self.client.start_channels()
        asyncio.ensure_future(self.execute())

    async def execute(self):
        self.client.execute(CODE)
        response = self.client.get_shell_msg()
        print("Before")
        res = await response
        print("After", res)


def main():
    app = QApplication(sys.argv)
    loop = qasync.QEventLoop(app)
    asyncio.set_event_loop(loop)
    test = Test()
    asyncio.ensure_future(test.start())
    with loop:
        loop.run_forever()


if __name__ == "__main__":
    main()