title: How to update IAM Policy using Boto3 Python
body: <p>I have a S3 bucket read policy : </p>
  
  <pre><code>   {
        "Version":"2012-10-17",
        "Statement":[
          {
            "Effect":"Allow",
            "Action":["s3:GetObject"],
            "Resource":["arn:aws:s3:::examplebucket/*"]
          }
        ]
      }
  </code></pre>
  
  <p>Based on a cloud trail logs when new bucket is created , I am creating an event which will invoke a Lambda function.</p>
  
  <p>Able to read json for the policy and add a new resource (bucket) to the same policy. Is there a direct python API to be invoked which will update an existing IAM policy with new resource ?</p>