Andrew Ng机器学习专项课程Lab运行pyvirtualdisplay遇WinError2错误求助

正在学习Andrew Ng的2022机器学习专项课程，在课程3第3周实验中执行以下代码：

from pyvirtualdisplay import Display
Display(visible=0, size=(840, 480)).start();

在Jupyter中运行该单元格时出现如下错误：

FileNotFoundError                         Traceback (most recent call last)
Input In [2], in <cell line: 2>()
      1 # Set up a virtual display to render the Lunar Lander environment.
----> 2 Display(visible=0, size=(840, 480)).start();
      4 # Set the random seed for TensorFlow
      5 tf.random.set_seed(utils.SEED)

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\pyvirtualdisplay\display.py:54, in Display.__init__(self, backend, visible, size, color_depth, bgcolor, use_xauth, retries, extra_args, manage_global_env, **kwargs)
     51 if not cls:
     52     raise ValueError("unknown backend: %s" % self._backend)
---> 54 self._obj = cls(
     55     size=size,
     56     color_depth=color_depth,
     57     bgcolor=bgcolor,
     58     retries=retries,
     59     use_xauth=use_xauth,
     60     # check_startup=check_startup,
     61     extra_args=extra_args,
     62     manage_global_env=manage_global_env,
     63     **kwargs
     64 )

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\pyvirtualdisplay\xvfb.py:44, in XvfbDisplay.__init__(self, size, color_depth, bgcolor, use_xauth, fbdir, dpi, retries, extra_args, manage_global_env)
     41 self._fbdir = fbdir
     42 self._dpi = dpi
---> 44 AbstractDisplay.__init__(
     45     self,
     46     PROGRAM,
     47     use_xauth=use_xauth,
     48     retries=retries,
     49     extra_args=extra_args,
     50     manage_global_env=manage_global_env,
     51 )

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\pyvirtualdisplay\abstractdisplay.py:85, in AbstractDisplay.__init__(self, program, use_xauth, retries, extra_args, manage_global_env)
     82 self._pipe_wfd = None
     83 self._retries_current = 0
---> 85 helptext = get_helptext(program)
     86 self._has_displayfd = "-displayfd" in helptext
     87 if not self._has_displayfd:

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\pyvirtualdisplay\util.py:13, in get_helptext(program)
      6 cmd = [program, "-help"]
      8 # py3.7+
      9 # p = subprocess.run(cmd, capture_output=True)
     10 # stderr = p.stderr
     11 
     12 # py3.6 also
---> 13 p = subprocess.Popen(
     14     cmd,
     15     stdout=subprocess.PIPE,
     16     stderr=subprocess.PIPE,
     17     shell=False,
     18 )
     19 _, stderr = p.communicate()
     21 helptext = stderr.decode("utf-8", "ignore")

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\subprocess.py:858, in Popen.__init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags, restore_signals, start_new_session, pass_fds, encoding, errors, text)
    854         if self.text_mode:
    855             self.stderr = io.TextIOWrapper(self.stderr,
    856                     encoding=encoding, errors=errors)
---> 858     self._execute_child(args, executable, preexec_fn, close_fds,
    859                         pass_fds, cwd, env,
    860                         startupinfo, creationflags, shell,
    861                         p2cread, p2cwrite,
    862                         c2pread, c2pwrite,
    863                         errread, errwrite,
    864                         restore_signals, start_new_session)
    865 except:
    866     # Cleanup if the child failed starting.
    867     for f in filter(None, (self.stdin, self.stdout, self.stderr)):

File D:\ProgramData\Anaconda3\envs\ML\lib\site-packages\subprocess.py:1311, in Popen._execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, unused_restore_signals, unused_start_new_session)
   1309 # Start the process
   1310 try:
-> 1311     hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
   1312                              # no special security
   1313                              None, None,
   1314                              int(not close_fds),
   1315                              creationflags,
   1316                              env,
   1317                              cwd,
   1318                              startupinfo)
   1319 finally:
   1320     # Child is launched. Close the parent's copy of those pipe
   1321     # handles that only the child should have open.  You need
   (...)
   1324     # pipe will not close when the child process exits and the
   1325     # ReadFile will hang.
   1326     self._close_pipe_fds(p2cread, p2cwrite,
   1327                          c2pread, c2pwrite,
   1328                          errread, errwrite)

FileNotFoundError: [WinError 2] The system cannot find the specified.

尝试修改subprocess.py源码将shell参数从False改为True，引发其他错误，不敢继续修改源码，寻求解决方案。

解决思路 #

1. 根本原因 #

pyvirtualdisplay默认依赖Xvfb后端，而Xvfb是Linux/Unix系统专属的虚拟X服务器，Windows系统原生不支持，这才是报错的核心，和subprocess的shell参数无关。

2. 可行方案 #

方案一：使用Windows兼容的虚拟显示后端

指定dummy后端绕过Xvfb调用，代码修改为：

from pyvirtualdisplay import Display
Display(backend='dummy', visible=0, size=(840, 480)).start();

方案二：直接禁用虚拟显示（仅运行环境无需可视化）

如果实验只需要运行Lunar Lander环境、不需要渲染画面，可直接注释掉虚拟显示代码：

# 注释掉虚拟显示相关代码
# from pyvirtualdisplay import Display
# Display(visible=0, size=(840, 480)).start();

# 继续后续实验代码
tf.random.set_seed(utils.SEED)

方案三：安装Windows版X服务器（需可视化场景）

1. 安装VcXsrv Windows X服务器，启动时选择「Multiple windows」「Start no client」，勾选「Disable access control」
2. 在Jupyter中添加环境变量配置后再调用pyvirtualdisplay：

import os
os.environ['DISPLAY'] = ':0'  # 与VcXsrv显示编号对应

from pyvirtualdisplay import Display
Display(visible=0, size=(840, 480)).start();

3. 注意事项 #

• 不要修改subprocess源码，会破坏Python标准库稳定性，引发更多不可预知问题。
• 课程实验默认基于Linux环境设计，Windows用户需做适配调整。

内容的提问来源于stack exchange，提问作者yishifeng