使用PhaseMap包遇asyncio事件循环已运行错误求修复方案

我正尝试使用PhaseMap这个Python包，但官方教程中的最小可运行示例无法正常执行：

import phasemap as pm

def phase(pos):
    x, y = pos
    return int(x**2 + y**2 < 1)

res = pm.run(
    phase,
    limits=[(-1, 1), (-1, 1)],
    mesh=3,
)

在Python 3.11.9环境下运行该代码时，触发如下错误：

File ~/Desktop/repos/non_linear_topological_invariants/nonlinear_topological_invariants/lib/python3.11/site-packages/phasemap-1.0.0-py3.11.egg/phasemap/_run.py:103, in run(fct, limits, mesh, num_steps, all_corners, init_result, save_file, load, load_quiet, serializer, save_interval)
     90 else:
     91     init_points = None
     93 return _RunImpl(
     94     fct=fct,
     95     limits=limits,
     96     mesh=mesh,
     97     num_steps=num_steps,
     98     all_corners=all_corners,
     99     init_points=init_points,
    100     save_file=save_file,
    101     serializer=serializer,
    102     save_interval=save_interval,
--> 103 ).execute()

File ~/Desktop/repos/non_linear_topological_invariants/nonlinear_topological_invariants/lib/python3.11/site-packages/phasemap-1.0.0-py3.11.egg/phasemap/_run.py:158, in _RunImpl.execute(self)
    157 def execute(self):
--> 158     self._loop.run_until_complete(self._run())
    159     return self.result

File ~/.pyenv/versions/3.11.9/lib/python3.11/asyncio/base_events.py:630, in BaseEventLoop.run_until_complete(self, future)
    619 """Run until the Future is done.
    620 
    621 If the argument is a coroutine, it is wrapped in a Task.
   (...)    627 Return the Future's result, or raise its exception.
    628 """
    629 self._check_closed()
--> 630 self._check_running()
    632 new_task = not futures.isfuture(future)
    633 future = tasks.ensure_future(future, loop=self)

File ~/.pyenv/versions/3.11.9/lib/python3.11/asyncio/base_events.py:589, in BaseEventLoop._check_running(self)
    587 def _check_running(self):
    588     if self.is_running():
--> 589         raise RuntimeError('This event loop is already running')
    590     if events._get_running_loop() is not None:
    591         raise RuntimeError(
    592             'Cannot run the event loop while another loop is running')

RuntimeError: This event loop is already running

该问题似乎与asyncio库的实现相关，但不知如何修复，请问是否有针对该包的直接修复方案？

这个错误是因为PhaseMap内部的asyncio事件循环管理在Python 3.11+环境下和已有运行中的事件循环冲突导致的，以下是几种直接修复方案：

方案1：修改PhaseMap源码适配事件循环 #

找到安装的PhaseMap包中的phasemap/_run.py文件，修改execute方法：

1. 原代码：

def execute(self):
    self._loop.run_until_complete(self._run())
    return self.result

2. 替换为：

import asyncio
import nest_asyncio

def execute(self):
    try:
        loop = asyncio.get_running_loop()
        if loop.is_running():
            nest_asyncio.apply()
            task = loop.create_task(self._run())
            loop.run_until_complete(task)
        else:
            self._loop.run_until_complete(self._run())
    except RuntimeError:
        self._loop.run_until_complete(self._run())
    return self.result

执行前先安装依赖包：pip install nest_asyncio

方案2：手动用异步模式调用（不修改包源码） #

直接在自己的代码中绕开pm.run的事件循环冲突问题：

import phasemap as pm
import asyncio
import nest_asyncio

def phase(pos):
    x, y = pos
    return int(x**2 + y**2 < 1)

async def run_phasemap():
    runner = pm._RunImpl(
        fct=phase,
        limits=[(-1, 1), (-1, 1)],
        mesh=3,
    )
    await runner._run()
    return runner.result

nest_asyncio.apply()
res = asyncio.run(run_phasemap())

方案3：降级Python版本 #

如果不想修改代码或添加依赖，可以暂时降级到Python 3.10及以下版本，该版本的asyncio事件循环检测逻辑不会触发这个错误。

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