Here's a nice example of a progressbar written in Python: http://nadiana.com/animated-terminal-progress-bar-in-python
But if you want to write it yourself. You could use the curses module to make things easier :)
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Perhaps easier is not the word for curses. But if you want to create a full-blown cui than curses takes care of a lot of stuff for you.
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Since the old link is dead I have put up my own version of a Python Progressbar, get it here: https://github.com/WoLpH/python-progressbar
