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Instantiating sub-class from super


On 2019-10-19 12:37 AM, DL Neil via Python-list wrote:
> On 16/10/19 6:33 PM, Frank Millman wrote:
>> On 2019-10-14 10:55 PM, DL Neil via Python-list wrote:
>>> Is there a technique or pattern for taking a (partially-) populated 
>>> instance of a class, and re-creating it as an instance of one of its 
>>> sub-classes?
> 
>> Here is a link to an article entitled 'Understanding Hidden Subtypes'. 
>> It dates back to 2004, but I think it is still relevant. It addresses 
>> precisely the issues that you raise, but from a data-modelling 
>> perspective, not a programming one.
>>
>> http://tdan.com/understanding-hidden-subtypes/5193
>>
>> I found it invaluable, and applied the concepts in my own 
>> business/accounting application. Having created the ability to make 
>> subtypes visible and explicit, I found all kinds of unexpected uses 
>> for them.
>>
>> The article seems to be missing a couple of images (Figure 1 and 
>> Figure 2) showing the data relationships. I downloaded the original 
>> article onto my computer years ago, and my local copy does have the 
>> images, so if you would like to see them let me know and I will upload 
>> my version somewhere to make it accessible.
> 
> Superb!
> 
> Yes please Frank - I've also approached it from the data/DB side, and 
> thus presumably why I was puzzling over how one implements in Python.
> 
> (alternatively, email a PDF/similar directly)

Hi

I have just got back from a few days break and have only seen your 
message now.

Did you see the message I posted on the 17th with a download link? If 
not, would you like me to post it again?

Frank