Purpose of Python Type Checking?

[Frodo Morris]

Mongryong wrote:
> Why do people use type checking in Python?  
> 
> Yes, I know its to "ensure" that parameters are valid but doesn't that
> defeat the whole purpose of one of Python's main feature? Polymorphism
> and code reuse.
[I know this is only *just* on-topic, but felt that someone had to say it]
Polymorphism and code re-use, the *two* main features of Python. 
Polymorphism, code re-use and readability.  The three main features of 
Python are: oh bugger, I'll come in again.
[You are now returned to your normal schedule]
-- 
FM