PermissionError: [WinError 32] 用于创建文件

Question

有一段代码如下

try:
    f = h5py.File(filename, 'w-')
except: 
    os.remove(filename)
    f = h5py.File(filename, 'w-')  

运行程序得到与上述代码段相关的错误。我认为这是因为文件没有关闭。 google了一下类似的错误信息，貌似可以解决using "with" statement，但是不知道上面代码段怎么修改。

OSError                                   Traceback (most recent call last)
<ipython-input-19-1f1f9c5eb3dd> in vid_to_hdf(En, start, end, chunk)
      9     try:
---> 10         f = h5py.File(filename, 'w-')
     11     except:

~\AppData\Local\Continuum\anaconda3\envs\fastai-py37\lib\site-packages\h5py\_hl\files.py in __init__(self, name, mode, driver, libver, userblock_size, swmr, rdcc_nslots, rdcc_nbytes, rdcc_w0, track_order, **kwds)
    407                                fapl, fcpl=make_fcpl(track_order=track_order),
--> 408                                swmr=swmr)
    409 

~\AppData\Local\Continuum\anaconda3\envs\fastai-py37\lib\site-packages\h5py\_hl\files.py in make_fid(name, mode, userblock_size, fapl, fcpl, swmr)
    176     elif mode in ['w-', 'x']:
--> 177         fid = h5f.create(name, h5f.ACC_EXCL, fapl=fapl, fcpl=fcpl)
    178     elif mode == 'w':

h5py\_objects.pyx in h5py._objects.with_phil.wrapper()

h5py\_objects.pyx in h5py._objects.with_phil.wrapper()

h5py\h5f.pyx in h5py.h5f.create()

OSError: Unable to create file (file exists)

During handling of the above exception, another exception occurred:

PermissionError                           Traceback (most recent call last)
<timed eval> in <module>

<ipython-input-19-1f1f9c5eb3dd> in vid_to_hdf(En, start, end, chunk)
     10         f = h5py.File(filename, 'w-')
     11     except:
---> 12         os.remove(filename)
     13         f = h5py.File(filename, 'w-')
     14     # Create dataset within file

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'E23.hdf5'

Answer 1

首先，在使用之前尝试删除文件。
如果你不能这样做，请尝试读取文件的内容，删除 File 对象，删除文件然后写入文件。

如果这不起作用，试试这个：

with h5py.File(filename, 'w-') as f:
    # This is where you put what you're going to do with f
# At the end of the with statement, the object gets deleted.
try:
    os.remove(filename)
except:
    pass

Answer 2

附带说明，共享代码示例中有些地方不清楚：

try:
    f = h5py.File(filename, 'w-')
except: 
    os.remove(filename)
    f = h5py.File(filename, 'w-')  # <- why the error handling code is repeating exactly as the code that just failed to run?

当打开系统资源（如文件）时，会存储有关该资源的信息/状态，这些信息/状态应作为程序的干净行为释放/关闭（例如关闭操作系统的文件句柄）。

所以在 Python 中

my_file = open('myfile.txt', 'r')  # getting the resource
my_file.readlines()  # using the resources
my_file.close()  # closing the file, releasing system resources

为了更容易做到这一点，一些 API 提供了一个 context manager，可以在 with 块中使用：

with open('myfile.txt', 'r') as my_file:
   my_file.readlines()

# after the with block, the context manager automatically calls close() when exiting the runtime context

h5pyprovides 这样的 API，所以 h5py.File 实例也可以在 with 块中使用：

with h5py.File(filename, 'w-') as f:
    pass # do your processing with f

# now after the block, the file is closed

请注意，关闭文件并不意味着删除它。因此，在代码中关闭文件并释放系统资源后，文件将保留在磁盘上，直到被删除。但在许多情况下，这是预期的行为，因为文件是程序的结果。

如果您想确保文件始终被删除，您可以使用try/finally 块，但请注意，在您的程序运行后，磁盘上不会有任何文件：

try:
   with f = h5py.File(filename, 'w-'):
       pass # use the file resource
finally:
   if os.path.exists(filename):
       os.remove(filename)