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[Python-Dev] PEP 575: Unifying function/method classes

Jeroen Demeyer J.Demeyer at UGent.be
Sun Apr 15 08:50:14 EDT 2018 
On 2018-04-14 23:14, Guido van Rossum wrote:
> That actually sounds like a pretty big problem. I'm sure there is lots
> of code that doesn't *just* duck-type nor calls inspect but uses
> isinstance() to decide how to extract the desired information.

In the CPython standard library, the *only* fixes that are needed 
because of this are in:

- inspect (obviously)
- doctest (to figure out the __module__ of an arbitrary object)
- multiprocessing.reduction (something to do with pickling)
- xml.etree.ElementTree (to determine whether a certain method was 
overridden)
- GDB support

I've been told that there might also be a problem with 
Random._randbelow, even though it doesn't cause test failures.

The fact that there is so little breakage in the standard library makes 
me confident that the problem is not so bad. And in the cases where it 
does break, it's usually pretty easy to fix.

Finally: changing the classes of certain objects is exactly the point of 
this PEP, so it's impossible to achieve 100% backwards compatibility.


Jeroen.
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