Windows下修复PyDub重开文件引发Errno 13权限错误的稳健方案

问题场景与报错信息 #

我正在学习PyDub，首个练习是播放WAV文件，适配后的代码如下。当前重点解决执行play(wav_file)时出现的[Errno 13]错误，暂不关注警告：

>>> import os
>>> os.chdir('C:/cygwin64/home/User.Name/Some.Path')
>>> from pydub import AudioSegment
>>> from pydub.playback import play
>>> wav_file = AudioSegment.from_file(file = "SomeFile.wav", format = "wav")

C:\Users\User.Name\anaconda3\envs\py39\lib\site-packages\pydub\utils.py:170: RuntimeWarning: Couldn't find ffmpeg or avconv - defaulting to ffmpeg, but may not work
  warn("Couldn't find ffmpeg or avconv - defaulting to ffmpeg, but may not work", RuntimeWarning)

>>> play(wav_file)

C:\Users\User.Name\anaconda3\envs\py39\lib\site-packages\pydub\utils.py:184: RuntimeWarning: Couldn't find ffplay or avplay - defaulting to ffplay, but may not work
  warn("Couldn't find ffplay or avplay - defaulting to ffplay, but may not work", RuntimeWarning)
Traceback (most recent call last):

  Cell In[5], line 1
    play(wav_file)

  File ~\anaconda3\envs\py39\lib\site-packages\pydub\playback.py:71 in play
    _play_with_ffplay(audio_segment)

  File ~\anaconda3\envs\py39\lib\site-packages\pydub\playback.py:15 in _play_with_ffplay
    seg.export(f.name, "wav")

  File ~\anaconda3\envs\py39\lib\site-packages\pydub\audio_segment.py:867 in export
    out_f, _ = _fd_or_path_or_tempfile(out_f, 'wb+')

  File ~\anaconda3\envs\py39\lib\site-packages\pydub\utils.py:60 in _fd_or_path_or_tempfile
    fd = open(fd, mode=mode)

PermissionError: [Errno 13] Permission denied: 'C:\\Users\\User.Name\\AppData\\Local\\Temp\\tmpryjpscsv.wav'

问题分析 #

已确认用户账户拥有Temp文件夹写入权限，经搜索得知Windows下重复打开未关闭的文件可能导致该错误。堆栈跟踪最后指向utils.py第60行，此处存在重复打开风险：

/c/Users/User.Name/anaconda3/envs/py39/lib/site-packages/pydub/utils.py
-----------------------------------------------------------------------
53 def _fd_or_path_or_tempfile(fd, mode='w+b', tempfile=True):
54     close_fd = False
55     if fd is None and tempfile:
56         fd = TemporaryFile(mode=mode)
57         close_fd = True
58
59     if isinstance(fd, basestring):
60         fd = open(fd, mode=mode)
61         close_fd = True
62
63     try:
64         if isinstance(fd, os.PathLike):
65             fd = open(fd, mode=mode)
66             close_fd = True
67     except AttributeError:
68         # module os has no attribute PathLike, so we're on python < 3.6.
69         # The protocol we're trying to support doesn't exist, so just pass.
70         pass
71
72     return fd, close_fd

修改尝试与疑问 #

注意到当fd被赋值为打开的文件时，close_fd标志会设为True，可借此避免重复打开。第60和65行是[Errno 13]的潜在触发点，考虑将前置if条件修改为以下形式，不确定是否稳健：

59     if not close_fd and isinstance(fd, basestring):
64         if not close_fd and isinstance(fd, os.PathLike):

第二个条件涉及os.PathLike，暂未完全理解其含义及外层try块的作用，但希望微观逻辑足够通用。

补充说明：已按上述方式修改第59和64行，但问题未解决，行为无变化。不想采用提前关闭文件的方案，因TemporaryFile()创建的临时文件关闭后会消失；且第60行执行前fd只是字符串，第56行执行前fd为None，无法关闭；此外close_fd标志的设计显然希望延迟关闭文件。

内容的提问来源于stack exchange，提问作者user2153235