First you need to install freetype2 and harfbuzz. then You can install pyharfbuzz using pip:
pip install pyharfbuzz
Use shape function to shape your text text:
from pyharfbuzz import shape
your_shaped_text_info = shape('Vazir.ttf', 'your text')
To use lower level APIs see example.py.
Open an issue if you need any harfbuzz API that pyharfbuzz doesn't support.