Python is a dynamic language where everything happens at run time, including checks of variable types. So you can already do this.
The problem with runtime is when you make a mistake it can be a long time before you find out. Compile time means a large class of problems is prevented without perfect test coverage. On a small project it isn't a big deal but when you have hundgeds of developers over decades you will miss something
Python has static typechecking which, while not perfect, works pretty well as long as you're not actually trying to circumvent it (or manipulating things "too dynamically")