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Numpy for array manipulations Pandas for CSV file manipulations Tkinter for GUI I've used these untill now. Python is having lots and lots of modules. Better to learn what is relavant to your project.
These are relatively simple: math, time, random This can be useful: numpy numpy offer an iterable that is very similar to lists: https://www.sololearn.com/learn/6671/?ref=app
If you are working with files: shutil os If you are doing scientific computing: scipy numpy (matplotlib) If you are working with text/pattern matching: re If you are working with machine learning: numpy (scipy) scikit-learn (tensorflow for advanced) matplotlib (seaborn) pandas If you want to make a GUI: tkinter (pyqt is better-looking but I think tkinter is better for beginners) If you want to make a website: django or flask