Abstract classes and PyMongo; can't instantiate abstract class

Question

I created the empty abstract class AbstractStorage and inherited the Storage class from it:

import abc
import pymongo as mongo

hos         


        

Answer 1

This isn't really a problem with ABCs, it's a problem with PyMongo. There is an issue about it here. It seems that pymongo overrides __getattr__ to return some sort of database class. This means that host.__isabstractmethod__ returns a Database object, which is true in a boolean context. This cause ABCMeta to believe that host is an abstract method:

>>> bool(host.__isabstractmethod__)
True

The workaround described in the issue report is to manually set host.__isabstractmethod__ = False on your object. The last comment on the issue suggests a fix has been put in for pymongo 3.0.