python : redirect output to text file and display it in real time

Question

I have a python function that calls many services, and prints results of the services called in a log file. this is my code :

def coordinator():
   f = file(path,'a')
   sys.stdout = f
   /* do a lot of stuff */
   f.close()
   with open(path) as log:
        logs = log.read()
        return jsonify(log = logs)

The result of the function is returned to a jQuery getJSON function that displays the final log file in a web page :

$.getJSON('/../coordinator',
  {//parameters},
  function(data) {
    //display data.log
  }
);

My problem is that the user gets to see the log file only when the execution is finished. Is there a way to display logs as they are written in real time??

Answer 1

Python's stdout is buffered, so it won't write until the buffer is full. To force an immediate write, use sys.stdout.flush() , or f.flush() in the case of your code.

Answer 2

I finally found what I was looking for here :

http://blog.miguelgrinberg.com/post/easy-websockets-with-flask-and-gevent

So basically I created a WebSocket between the Back-end (Python/Flask) and the Front-end (HTML, jquery) to ensure continuous communication.

And with Python I created a Thread that runs asynchronously with the Master thread, fetches repetitively the content of the log file and sends them to Jquery via ajax