[Tutor] What are the benefits of template or abstract base classes?

[boB Stepp]

Now in "4.2 Inheritance" at
https://dabeaz-course.github.io/practical-python/Notes/04_Classes_objects/02_Inheritance.html

class TableFormatter:
     def headings(self, headers):
         '''
         Emit the table headings.
         '''
	raise NotImplementedError()

     def row(self, rowdata):
         '''
         Emit a single row of table data.
         '''
	raise NotImplementedError()

with the comment:

"This class does nothing, but it serves as a kind of design specification
for additional classes that will be defined shortly. A class like this is
sometimes called an “abstract base class.”"

As the exercises in this section progressed I had to write the classes
TextTableFormatter(TableFormatter), CSVTableFormatter(TableFormatter) and
HTMLTableFormatter(TableFormatter) for which each class had its custom
implementations of the headings and row methods.  I don't see much real
benefit to having the original TableFormatter class as used here.  Am I
wrong to think this?  At best it gives a single place to look to remind a
coder what methods are intended to be implemented for all subclasses, but
does not constrain the coder to do so.

OTOH, this inspired me to read up a bit on actual abstract base classes
(ABC), which *do* force the coder to implement the methods of the ABC or it
will not allow one to instantiate the method-deficient subclass.  I can see
some benefit to this approach.  Of course, Beazley may be planning on
heading in the true ABC direction later in the material.

What are your thoughts?  Perhaps a fuller explanation for noobie boB?

-- 
Wishing you only the best,

boB Stepp