Call python function from JS

Apart from the mentioned points and assuming you already have a proper setup to serve your python script and return the response. You should submit an asynchronous request, especially if the python code does some heavy computation.

function postData(input) {
    $.ajax({
        type: "POST",
        url: "/reverse_pca.py",
        data: { param: input },
        success: callbackFunc
    });
}

function callbackFunc(response) {
    // do something with the response
    console.log(response);
}

postData('data to process');

If you only do some light computation and you have no problem working with a code deprecated as of jQuery 1.8, go with the synchronous approach. This is not recommended as it blocks the main thread.

function runPyScript(input){
    var jqXHR = $.ajax({
        type: "POST",
        url: "/reverse_pca.py",
        async: false,
        data: { param: input }
    });

    return jqXHR.responseText;
}

// do something with the response
response= runPyScript('data to process');
console.log(response);

Read more about it here: How do I return the response from an asynchronous call? and http://api.jquery.com/jquery.ajax/