title: Numpy array concatenate: ValueError: all the input array dimensions for the concatenation axis must match exactly
body: <p>How to concatenate these NumPy arrays?</p>
  <p>first array with a shape (3951, 400)
  second array with a shape (4939, 4)</p>
  <p>I tried <code>np.concatenate((array1, array2), axis=1)</code>
  and I tried another solution like in this question  <a href="https://stackoverflow.com/questions/41989950/numpy-array-concatenate-valueerror-all-the-input-arrays-must-have-same-number">numpy array concatenate: &quot;ValueError: all the input arrays must have same number of dimensions&quot;</a> but I get this error</p>
  <p>ValueError: all the input array dimensions for the concatenation axis must match exactly, but along dimension 0, the array at index 0 has size 3951 and the array at index 1 has size 4939</p>