I knew before that print in Python had some weird properties. Like:

>>> for i in [1, 2, 3, 4]:
... print "blah"
...
blah
blah
blah
blah
>>> for i in [1, 2, 3, 4]:
... print "blah",
...
blah blah blah blah


One thing you’ll notice is that there’s a space between each of the blahs. If you don’t want those spaces, you need to use sys.write. Here’s an example of using sys.write along with a progress bar indicator. Which is exactly what I wanted this for.

Finally, you can indicate to python on the command-line that you want unbuffered stdin and stdout with python -u.