Hi Rahul, thanks for asking,


> I was going through the chapter as per the below link :
> https://docs.python.org/3/tutorial/errors.html#handling-exceptions
> [...]
> I think this elaboration needs to be done.
>
> I would request you to provide your insights on this.

A simple way to think of it is to remember the exception hiearchy: https://docs.python.org/3/library/exceptions.html?highlight=baseexception#exception-hierarchy

For example, here, ArithmeticError inherits Exception, it's more specific, and ZeroDivisionError inherits from ArithmeticError, is really specific. So we have something like:

class ArithmeticError(Exception):
    pass

class ZeroDivisionError(ArithmeticError):
    pass

expecting Exception will catch Exception, ArithmeticError and ZeroDivisionError
expecting ArithmeticError will catch ArithmeticError and ZeroDivisionError
expecting ZeroDivisionError will only catch ZeroDivisionError.

Back to the example with B, C, D: D is the most specific, and B the most generic exception, so writing:

    except D:
        print("D")
    except C:
        print("C")
    except B:
        print("B")

tries the most specific first, which have a chance to catch D.

writing it the other way around, we're getting "except B" first, the generic one, which will catch B, C, and D, thus printing B three times.

Hope it helps,

Bests,
-- 
Julien Palard
https://mdk.fr