parsed_json = json.loads(request.body)

$("#add_user_button").click(function (event) {
    event.preventDefault();
    $.ajax({
        type: "POST",
        url: '/user/',
        data:
            {
                'action': "addUser",
                'username': $('#id_username').val(),
                'password': $('#id_password').val(),
                'groups': $('#id_groups').val()
            }
        ,
        contentType: 'application/json; charset=utf-8',
        processData: false,
    });
}

print(request.POST.get("username"))
#print(request.encoding) #returns none
print("Request body is :")
print(request.body)
print(type(request.body))

hello
Request body is :
b'username=hello&password=world&csrfmiddlewaretoken=&addUser=Add+User'
<class 'bytes'>