Mypy is an optional static type checker for Python. You can add type hints (PEP 484) to your Python programs, and use mypy to type check them statically. Find bugs in your programs without even running them! You can mix dynamic and static typing in your programs. You can always fall back to dynamic typing when static typing is not convenient, such as for legacy code. This (source) is downloaded from pypi.org/projects/mypy as the mypi github site does not have a complete sourcecode zip. This requires typing-extensions created with python3 present.