Cannot pass an argument to python with "#!/usr/bin/env python"
In some environment, env doesn't split arguments.So your env is looking for python -u in your path.We can use sh to work around.Replace your shebang with the following code lines and everything will be fine.
#!/bin/sh''''exec python -u -- "$0" ${1+"$@"} # '''# vi: syntax=pythonp.s. we need not worry about the path to sh, right?
It is better to use environment variable to enable this. See python doc : http://docs.python.org/2/using/cmdline.html
for your case:
export PYTHONUNBUFFERED=1script.py