Why does print run only after executing for loop in Python

Question

Suppose I have a for loop. 

for i in range(10):
    print(i)

So now instead of printing the numbers from 0 to 9 one by one, python waits and prints them all at once. I want to know why is this happening. 

Answer 1

Your stdout is line-buffered; this means that it won't show the text until a newline is encountered. To solve this, you need to explicitly flush the buffer.

import sys
for i in range(10):
    print(i)
sys.stdout.flush()