运行pytest时遇AttributeError：_UnixSelectorEventLoop无_signal_handlers属性

错误信息 #

Connected to pydev debugger (build 233.15026.15)
Exception ignored in: <function BaseEventLoop.__del__ at 0x12809be50>
Traceback (most recent call last):
  File "/usr/local/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/base_events.py", line 688, in __del__
    self.close()
  File "/usr/local/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/unix_events.py", line 60, in close
    for sig in list(self._signal_handlers):
AttributeError: '_UnixSelectorEventLoop' object has no attribute '_signal_handlers'
Exception ignored in: <function BaseEventLoop.__del__ at 0x12809be50>
Traceback (most recent call last):
  File "/usr/local/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/base_events.py", line 688, in __del__
    self.close()
  File "/usr/local/Cellar/python@3.9/3.9.19/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/unix_events.py", line 60, in close
    for sig in list(self._signal_handlers):
AttributeError: '_UnixSelectorEventLoop' object has no attribute '_signal_handlers'
Launching pytest with arguments <args here>

解决方案 #

• 升级PyCharm：该错误源于PyCharm调试器（pydev）与M1架构下Python 3.9 asyncio的兼容性问题，更新至2024.x及以上版本的PyCharm可直接修复。
• 更换Python解释器：
  1. 打开File > Settings > Project: [项目名] > Python Interpreter
  2. 替换为系统自带Python或通过conda创建适配M1的虚拟环境，避免使用Homebrew安装的Python 3.9（部分版本存在asyncio底层bug）
• 调整调试器配置：
  1. 进入Run > Edit Configurations
  2. 选中你的pytest配置，在Configuration页勾选Emulate terminal in output console
  3. 或添加环境变量PYDEVD_DISABLE_ASYNCIO_SUPPORT=1到配置的Environment variables中
• 手动初始化事件循环属性：在项目根目录的conftest.py中添加以下代码，提前初始化缺失的属性：

import asyncio
from asyncio import UnixSelectorEventLoop

def pytest_configure(config):
    loop = UnixSelectorEventLoop()
    if not hasattr(loop, '_signal_handlers'):
        loop._signal_handlers = {}
    asyncio.set_event_loop(loop)

内容的提问来源于stack exchange，提问作者prabodhprakash