title: saving dictionary into json python
body: <p>I am quite new to python and I was trying to make two arrays or matrices, register them into a dictionary, save to a json file. Here is my code</p>
  
  <pre><code>import numpy as np
  import json
  array_1 = np.array([[1,2,3],[4,6,7]])
  array_2 = np.array([[4,0],[9,8]])
  json_data = {
      'array_1': array_1,
      'array_2': array_2,
   }
  
  import json
  
  with open('json_data.json', 'wb') as fp:
      json.dumps(json_data, fp)
  </code></pre>
  
  <p>But I get the following error: </p>
  
  <blockquote>
    <p>Object of type 'ndarray' is not JSON serializable</p>
  </blockquote>