title: How to find and replace a part of a value in json file
body: <p>I have a json file that I am using as a Dictionary in python. 
  The json file is really long with 10k+ records. I need to replace the $home part in the "iscategorical" with the value of "id". After making the changes, I want to save this file so that I can use it again as a dictionary. Thank you for the help. Here is a sample:  </p>
  
  <pre><code>{
  "maps": [
      {
          "id": "xyzp",
          "iscategorical": "/u/$home/app/home"
      },
      {
          "id": "trtn",
          "iscategorical": "/u/app/$home/user"
      }
  ]}
  </code></pre>