Strange Python thread behavior

Question

EDIT : Actually what happened was that I ran it in Programmer's Notepad and it waited for the program to complete before capturing the stdout output and printing it to console, then I ran it from mingw which worked as expected. This behavior is obvious and expected, I just haven't realized that I was running the program in programmer's notepad rather than shell as I usually do. My bad.

---

I was playing with Python threads, but ran into this weird problem where if I have a print statement and a 1 second sleep statement inside the callback function, it doesn't do the printing until the sum of the sleep times has elapsed.

here is the code that causes this behavior:

import threading
import time

def callback():
    for i in range(3):
        print "Hello, World!";
        time.sleep(1)

myThread = threading.Thread (
    target = callback, 
    args = []
)

myThread.start()

This is how I want it to behave:

public class Demo
{    
    public static void main(String[] args)
    {
        (new Thread(() -> {
            for (int i = 0; i < 3; ++i) {
                System.out.println("Hello, World!");
                try {
                    Thread.sleep(1000);
                } catch(Exception e){
                    // rethrow as an unchecked exception but do not silence it.
                    throw (RuntimeException)e; 
                }
            }
        })).start();
    }
}

What is causing Python to behave this way, and how can I get it to behave the way I expect it to?

Answer 1

Based on your comments, I have a feeling that your problem is due to the system not flushing stdout. To fix it, try this:

import sys

Then right after your print function:

sys.stdout.flush()