I developed this library ( https://github.com/hhuuggoo/thedoctor ) to help deal with this problem. My belief is that type validation is only part of the problem - being guaranteed about properties of your inputs and outputs is also necessary (for example, make sure the input dataframes have datetime indices, and include the following columns, or ensure that this matrix is nonsingular). I have worked on some of the largest python projects at nyc investment banks, I think I've seen what I can safely call the scariest python project in the world

There is also another library out there which approaches the problem a bit differently

https://andreacensi.github.io/contracts/