Updating Key in JSON File

[decampo04]

Hi all, this is my first post as I am a Python beginner and would greatly appreciate any help. Basically, I need to update a a JSON file used by a service that contains a simple JSON list. However, rather than the values I need to replace the key names so the roles map to an Active Directory group within the sample file below:

Output:
{
  "operations": {
    "ops_modify": {
      "paths": [
        "ops_set_config"
      ],
      "methods": [
        "GET"
      ]
    },
    "ops_read": {
      "paths": [
        "ops_get_summary",
        "ops_get_request_info"
      ],
      "methods": [
        "GET"
      ]
    }
  },
  "roles": {
    "Server Op": [
      "emc",
      "mgmt",
      "fips_read"
    ],
    "Deployer": [
      "mgmt",
      "config"
    ],
    "KP Admin": [
      "mgmt",
      "kp"
    ]
  },
  "permissions": {
    "logs": [
      "ops_read",
      "file"
    ],
    "adminusers": [
      "adminusers.read"
    ]
  }
}

So, I need to replace the 'Deployer' role with an AD distinguished name such as 'CN=Dev_Deployer,OU=test,DC=example,DC=com'. I've already updated another JSON file using the json module but in that case I only needed to change the values against a key, not the key itself. I have managed to achieve the above by using the code below:

def replace_acls(self, filename, dn, role):
    with open(filename, 'r') as f:
        dn = f.read().replace(role, dn)

    with open(filename, 'w') as f:
        f.write(dn)

However, I'd like to follow best practice of using the JSON module instead but cannot get it to write the data back to the file. As an example of the code I cannot get to work:

import json

with open('acl.json', 'r') as f:
    data = json.load(f)
    for item in data['roles']:
        item = item.replace('Deployer', 'CN=Dev_Deployer,OU=test,DC=example,DC=com')

with open('acl.json', 'w') as f:
    json.dump(data, f, indent=2)

Any ideas, thanks in advance?