HDF5 file created with h5py can't be opened by h5py

Since we resolved the issue in the comments on my question, I'm writing the results out here to mark it as solved.

The main problem was that I forgot to close the file after I created it. There would have been two simple options, either:

import numpy as np
import h5py

f = h5py.File('myfile.hdf5','w')
group = f.create_group('a_group')
group.create_dataset(name='matrix', data=np.zeros((10, 10)), chunks=True, compression='gzip')
f.close()

or, my favourite because the file is closed automatically:

import numpy as np
import h5py

with h5py.File('myfile.hdf5','w') as f:
    group = f.create_group('a_group')
    group.create_dataset(name='matrix', data=np.zeros((10, 10)), chunks=True, compression='gzip')

I was working with https://github.com/matterport/Mask_RCNN and produced the same Error:

    Traceback (most recent call last):
  File "detection.py", line 42, in <module>
    model.load_weights(model_path, by_name=True)
  File "/home/michael/Bachelor/important/Cable-detection/Mask_RCNN-2.1/samples/cable/mrcnn/model.py", line 2131, in load_weights
    f = h5py.File(filepath, mode='r')
  File "/home/michael/.local/lib/python3.6/site-packages/h5py/_hl/files.py", line 271, in __init__
    fid = make_fid(name, mode, userblock_size, fapl, swmr=swmr)
  File "/home/michael/.local/lib/python3.6/site-packages/h5py/_hl/files.py", line 101, in make_fid
    fid = h5f.open(name, flags, fapl=fapl)
  File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper (/tmp/pip-s_7obrrg-build/h5py/_objects.c:2840)
  File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper (/tmp/pip-s_7obrrg-build/h5py/_objects.c:2798)
  File "h5py/h5f.pyx", line 78, in h5py.h5f.open (/tmp/pip-s_7obrrg-build/h5py/h5f.c:2117)
OSError: Unable to open file (Addr overflow, addr = 800, size=8336, eoa=2144)
HDF5: infinite loop closing library
      D,T,F,FD,P,FD,P,FD,P,E,E,SL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL,FL

The solution above worked for me too. I interrupted the training at a random point, therefor the .hdf5 file was not closed properly and could not be opened afterward.