How to flush the printed statements in IPython

Question

I want to print some debug statements during a loop in my function and I use IPython to call the function. Let an example function be:

def test_print():
    import time
    for i in range(5):
        time.sleep(2)
        print i,  time.time()

The result is like follows:

0 1372337149.84
1 1372337151.84
2 1372337153.85
3 1372337155.85
4 1372337157.85

I expect each row to be printed, then wait for 2 seconds. But the behavior is as follows. I first observe:

0 1372337149.84
1 

Then, after 2 seconds I observe the time stamp of 1 and the id of the next row, which is 2. I observe the last time stamp finally. I couldn't figure out why it behaves like this instead of one row at a time. Any thoughts? Do I need a special flush function to print what is waiting to be printed?

Answer 1

I've never used IPython, but it should suffice to flush stdout after each print statement.

Something like this ought to work...

def test_print():
    import time
    import sys
    for i in range(5):
        time.sleep(2)
        print i,  time.time()
        sys.stdout.flush()