Passing variables between Python and Javascript

Question

Imagine that you need to write some Javascript that simply changes a set of checkboxes when a drop down list is changed.

Depending on which item is selected in the list,

Answer 1

Funny, I've got web pages with JavaScript that talk to Python CGI modules that use SQLAlchemy.

What I do is send AJAX request but with JSON request in the body instead of XML. Python CGI modules use standard json module to deserialize JSON into a dictionary.

JavaScript side looks like this:

function on_request_success(response) {
    console.debug('response', response);
} 

function on_request_error(r, text_status, error_thrown) {
    console.debug('error', text_status + ", " + error_thrown + ":\n" + r.responseText);
}

var request = { ... };
jQuery.ajax({
    url: 'http://host/whatever.cgi',
    type: 'POST',
    cache: false,
    data: JSON.stringify(request),
    contentType: 'application/json',
    processData: false,
    success: on_request_success,
    error: on_request_error
});

And Python like this:

request = json.load(sys.stdin)
response = handle_request(request)
print("Content-Type: application/json", end="\n\n")
json.dump(response, sys.stdout, indent=2)

Note, it doesn't use Python cgi module, since the whole request is passed as JSON in the body.