It's also cultural, possibily. Python supports diamond inheritance, and clearly states how it handles it (it ends up virtual in C++ terms). But in like 20 years of working with Python I can't remember encountering diamond inheritance in the wild once.
Django documentation explicitly recommended it for a short while. At a point, the Python community created all kinds of mixins on all kinds of random APIs.
Diamond inheritance is in fact highly pervasive in Python. The reason is that every class is a subclass of object since Python 3 (Python 2 allows classic classes that are different). So every single time you use multiple inheritance you have diamond inheritance. Some of this diamond inheritance is totally innocuous, but mostly not, because a lot of classes override dunder methods on object like __setattr__. It was Guido van Rossum himself that observed the prevalence of diamond inheritance that led to Python 2.3 fixing the MRO, and introducing the super() function to make multiple inheritance sane.
> Diamond inheritance is in fact highly pervasive in Python.
I don't think that's true, because...
> So every single time you use multiple inheritance you have diamond inheritance.
Multiple inheritance is supported but not itself “highly pervasive” in Python
> It was Guido van Rossum himself that observed the prevalence of diamond inheritance
The essay you link does not support that claim. He doesn’t observe an existing prevalence, he describes new features being added simultaneously with the MRO fix that would present new use cases where diamond inheritance may be useful.
And, its true, diamond inheritance is more common in modern Python than it was with classic classes in ancient Python, but there is a huge leap between that and “highly pervasive”.
The MRO fix was added to Python 2.3. The new style classes that would cause diamond inheritance to be prevalent were already present in Python 2.2. So they weren’t simultaneous.
A better phrasing would be that Guido predicted the prevalence of diamond inheritance in Python and therefore found it necessary to fix the MRO.
