python 中的 HDF5：读取文件

Question

I have used this before with no problem, and it suddenly doesn't work:

import scipy.io
import numpy as np
import h5py
f = h5py.File('Dv25.mat','r')
D = f["Dv25"]

Output:

Traceback (most recent call last):

  File "C:/Users/jonathan/Documents/Forskning/P1/Datab/Felles/Matart/Felles/datab.py", line 5, in 
<module>
    D = f["Dv25"]
  File "h5py\_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
  File "h5py\_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
  File "C:\Program Files\Python38\lib\site-packages\h5py\_hl\group.py", line 264, in __getitem__
    oid = h5o.open(self.id, self._e(name), lapl=self._lapl)
  File "h5py\_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
  File "h5py\_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
  File "h5py\h5o.pyx", line 190, in h5py.h5o.open
KeyError: "Unable to open object (object 'Dv25' doesn't exist)"

However, typing f gives:

>>> f
<HDF5 file "Dv25.mat" (mode r)>

and exchanging Dv25.mat for Dv25 or using either ' or " doesn't help.

What's the reason for this problem and how can I fix it? Clearly this file is "there"

Thanks!!!

Best, J

Answer 1

Some h5py/HDF5 basics:
f is a file object.
f['Dv25'] is an object reference (either a group or dataset). In this case, it is a node named 'Dv25' at the root level ('/'). Apparently an object by this name doesn't exist in your file.
Use f.keys() to get objects at the root level. This will return a view of the root level objects; they could be groups or data sets. You can iterate on them to get the names. To print, use this loop: (that should identify the root level names):

for i in f.keys():  
    print (i)

Note: .mat extensions usually come from Matlab, which has an option to write HDF5 formatted files. Be sure this is written in that format.