Am I missing something with Python not having interfaces?

[Pete Forman]

I would suggest that using an interface at compile time is not the
only approach.  Unit tests can be run on classes to check that they do
indeed quack.
-- 
Pete Forman                -./\.-  Disclaimer: This post is originated
WesternGeco                  -./\.-   by myself and does not represent
pete.forman at westerngeco.com    -./\.-   the opinion of Schlumberger or
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