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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.os.vms
Subject: Re: VMS x86-64 database server
Date: Fri, 11 Jul 2025 02:54:36 -0000 (UTC)
Organization: A noiseless patient Spider
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On Thu, 10 Jul 2025 20:38:29 -0400, Arne Vajhøj wrote:

> The ability to subclass exceptions to catch specific and the ability
> to rethrow exceptions are quite common. Not Python specific at all.
>
> Java use sub-classing extensively for database. A little simplified:
>
>               |->SQLNonTransientException->non transient exception classses
> SQLException-|
>               |->SQLTransientException->transient exception classses
>

Python has metaclasses. These make it easy to set up an exception
hierarchy based on status codes (or other criteria). A subclass
definition can be as simple as

    class HangupNetworkTrouble(HangupCause) :
        _CODES_ = {2, 3, 38, 42}
    #end HangupNetworkTrouble

Now if the status code is one of those listed, any instantiation of
the base class will automatically delegate to this subclass.