#!/usr/bin/env python

import time
import sys

print 'Hello world! --> Python 2'
sys.stdout.flush()
print("Hello world! --> Python 3")
sys.stdout.flush()

time.sleep(1)

for i in range(5):
    print  '%d --> Python 2' % i
    sys.stdout.flush()
    print("%d --> Python 3") % i
    sys.stdout.flush()
    time.sleep(1)