tqdm
A Fast, Extensible Progress Bar for Python and CLI
...Just by inserting tqdm (or python -m tqdm) between pipes will pass through all stdin to stdout while printing progress to stderr.
tqdm does not require any dependencies, has a very low overhead and uses smart algorithms to predict the remaining time and skip unnecessary iteration displays. It works on just about any platform, console or in a GUI, as well as IPython/Jupyter notebooks.