Running a Python script with unbuffered output is often useful. For example, there's a script whose output I wish to examine as it produces data; or to ensure that if the program fails midway then the already computed result is printed. See Buffered vs Unbuffered I/O on StackOverflow.
There are several ways to do this:
python -u <script>
This run the Python in unbuffered so any lines will be written as soon as they are generated before continuining. Unfortunately, this doesn't work in a Shebang line (a limitation of shebang in general).
The second way is to open a file-handle in unbuffered more, which may appear to be more complicated than it should be. As usual, the best place to look for solutions is StackOverflow.
However, if you are running Python 3.3 or greater, you can use print with
flush=True option.
For example,
print("Hello World!", flush=True)
Happy hacking!