Python: Any way to declare constant parameters?

I have a method:

def foo(bar):
   # ...

Is there a way to mark bar as constant? Such as "The val开发者_如何学Cue in bar cannot change" or "The object pointed to by bar cannot change".

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If bar is an inmutable object, bar won't change during the function.

You can also create your own constant object. The recipe here.

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No.

What's the point? If you're writing the function, isn't it up to you to make sure bar doesn't change? Or if you're calling the function, who cares?