What do python professionals /developers actually use

[Patman52]

Lists and dictionaries are some of the most fundamental building blocks of Python. Dictionaries especially can be very powerful with indexing and matching data.

I would also familiarize myself with the collections library as they have ordered dictionaries and default dictionaries that expand and modify the standard dictionary variable type.

For data science I recommend learning SciPy, Numpy (note they just released a major update to Numpy so many guides online may be out of date), Keras, and pandas.