title: iteratively replace values in json file
body: <p>I have to perform some tests to tune some numeric parameters of a json file.
  To make simple, I replaced all these values by the string 'variable', then did the following:</p>
  
  <pre><code>numeric_vals = [10,20, 30, 40]  # numeric values to replace in that order 
  with open ('mypath') as my_file:
      json_str = my_file.read()
  for i in numeric_vals:
      json_str = json_str.replace("\"variable\"", str(i), 1)
  c = json.loads(json_str)  #loading in order to work with
  </code></pre>
  
  <p>This works fine, but is there a more efficient way to do this ? Values that need to be replaced are in variable depths, and may be inside lists etc. My json file is 15Kb and I need to test many (really many!) configurations. At each test, about 200 variables need to be replaced. I am on python 2.7 , but python 3.5 is also an option.
  Thanks for your help!</p>
  
  <p><strong>EDIT :</strong> </p>
  
  <p>here is a sample of my dict. It should be noted that the real thing is far longer and deeper:</p>
  
  <pre><code> {
  "1": {
      "transition": {
          "value": "variable", # edit here
          "unite": "sec"
      },
      "sequence": [
          {
              "step": "STEP",
              "name": "abc",
              "transition": {
                  "value": "variable", #edit here
                  "unite": "sec"
              },
              "entity": "aa",
              "_equipement": 3,
              "_value": 0
          },
          {
              "step": "FORK",
              "BRANCHES": [
                  {
                      "": {
                          "sequence": [
                              {
                                  "step": "STEP",
                                  "name": "klm",
                                  "transition": {
                                      "value": "variable", # edit here
                                      "unite": "sec"
                                  },
                                  "entity": "vvv",
                                  "_equipement": 10,
                                  "_value": 0,
                                  "conditions": [
                                      [
                                          {
                                              "name": "ddd",
                                              "type": "el",
                                              "_equipement": 7,
                                              "_value": 1
                                          }
                                      ]
                                  ]
                              }
                          ]
                      }
                  },
                  {
                      "SP": {
                          "sequence": [
                              {
                                  "step": "STEP",
                                  "name": "bbb",
                                  "transition": {
                                      "value": "variable", # edit here
                                      "unite": "sec"
                                  },
                                  "entity": "bb",
                                  "_equipement": 123,
                                  "_value": 0,
                                  "conditions": [
                                      [
                                          {
                                              "name": "abcd",
                                              "entity": "dgf",
                                              "type": "lop",
                                              "_equipement": 7,
                                              "_valeur": 0
                                          }
                                      ]
                                  ]
                              }
                          ]
                      }
                  }
              ]
          }
      ]
  }
  </code></pre>
  
  <p>}</p>