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  • Chris Kang thinks this is interesting:

Normally, a new-style class only extends at most one substantial built-in type—this means at most one built-in type in addition to object,

From

Cover of Python in a Nutshell, 3rd Edition

Note

Only try to extend from one build in type. No multiple inheritance from multiple build in type. Note that all objects inherit from "object" type. So, you can have one more build in type from which you can inherit, only if such inheritance is allowed by the build in type.