Post JSON to Python CGI

OK, let’s move to your updated question.

First, you should pass Ajax data property in string representation. Then, since you mix dataType and contentType properties, change dataType value to "json":

$.ajax({
    url: "saveList.py",
    type: "post",
    data: JSON.stringify({'param':{"hello":"world"}}),
    dataType: "json",
    success: function(response) {
        alert(response);
    }
});

Finally, modify your code a bit to work with JSON request as follows:

#!/usr/bin/python

import sys, json

result = {'success':'true','message':'The Command Completed Successfully'};

myjson = json.load(sys.stdin)
# Do something with 'myjson' object

print 'Content-Type: application/json\n\n'
print json.dumps(result)    # or "json.dump(result, sys.stdout)"

As a result, in the success handler of Ajax request you will receive object with success and message properties.