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CEFPython: Initiating a Python-based Web Service Call from within JavaScript

May 6, 2015 13:00
When developing an app with CEFPython, there may be many reasons you'd like to make a service call from Python.

  • Sensitive security credentials need to be sent
  • The service isn't simple to consume from JavaScript (e.g. SOAP)

If the service call takes a while, you may notice that the browser's UI hangs (I noticed this). I created a class to help handle the threading:
import requests
import threading

class ThreadedRequestHelper(threading.Thread):
    def __init__(self, external):
        self.external = external

    def SendRequestThread(self):
        #time.sleep(3)
        response = requests.post(self.url, json=self.json_obj)
        self.external.ExecuteFunction('OnStatesDataReceived', response.text)

    def SendRequest(self, url, json_obj):
        self.url = url
        self.json_obj = json_obj
        threading.Thread(target=self.SendRequestThread).start()
Note: This code is for a quick demo, so it was quickly thrown together. The sleep() function above is for testing, to see if the browser UI hangs while we're waiting.

The JavaScript handler in the Python code looks like this:
def GetStates(self, json_obj):
    request_helper = ThreadedRequestHelper(self)
    request_helper.SendRequest('http://localhost:9090/GetStates', json_obj)
We'll be calling the CherryPy service detailed here.

Our JavaScript looks like this:
$(document).ready(function() {
    $('#states-filter').on('keypress', function(e) {
        if(e.which == 13) {
            GetStates();
        }
    })

    $('#submitButton').on('click', function() {
        GetStates();
    });
});

function GetStates() {
    var request = {
        filter: $('#states-filter').val()
    };
    external.GetStates(request);
}

function OnStatesDataReceived(json_response) {
    var response = JSON.parse(json_response);

    var html = '';
    for(var i=0; i < response.length; i++) {
        html += '<li>' + response[i] + '</li>';
    }
    $('#states').html(html);
}
The full wxpython.py and some web files are attached below. Note that this is not all of the files necessary needed to run (as that is very large in size). 

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