Strict mode?

[Jack]

While enjoying the dynamic feature of Python I find it difficult to refactor 
code without breaking it. For example, if I modify a function to take more 
arguments, or arguments of different types, I'll need to manually find out 
all places where the function is called and make sure I modify them all, 
unlike in C/Java, where the compiler will do the work of checking function 
signatures, etc. I suppose there isn't a strict mode in Python. It would be 
helpful though, when I don't need things to be so dynamic, and this is often 
the case, when it comes to function arguments and return values, for 
example. Even a module level or function level flag would be very helpful to 
find broken code. Or, are there any third party tools that do this?