Unfortunately, those links don't give complete truth, because:

#class C(tuple, list):

class Foo1:
    pass
#    def __str__(self):
#        return "Foo1"

class Foo2:
    pass
    def __str__(self):
        return "Foo2"

class C(Foo1, tuple, Foo2):
    pass

t = C((1, 2, 3))
t.foo = "bar"
print(t)
print(t[0])
print(t.foo)

Foo2
1
bar

One would expect tuple's print to be used if real natural ordering is used. What logic CPython applies here? That builtin type's print used only if no user types provide it? (Supposedly to let user chance override it?) Is it applied only for special methods (like __str__ in this case), or for all methods? Questions, questions...

And that's exactly MRO non-compliance what hits:
https://mail.python.org/pipermail/python-dev/2014-April/134342.html

Righto. Well, if it's supposed to be that way, then it's going to be a hack to implement.

Seems that __add__ is correct (ie goes to built in).

Also seems that explicit t.__str__() calls Foo2's (so "incorrect").

And yet __repr__ will go to the tuple! (via both repr(t) and t.__repr__).

@dpgeorge , as reply to python-dev message above explains, this case is fully governed by C3 MRO algo. Then apparently CPy for a case where __str__ and __repr__ give the same result, implements just __repr__, and redirection __str__ -> __repr__ happens in object.__str__.

We surely don't need to either implement or emulate this __str__/__repr__ behavior, it's fair to call it impl-specific (those methods are "special", as we know). Other methods should not give such surprises. But the whole MRO issue of course would be (yet another) reason why Django isn't going to work anytime soon ;-).

I get:

>>> list.__str__
<slot wrapper '__str__' of 'object' objects>
>>> list.__repr__
<slot wrapper '__repr__' of 'list' objects>

Yup, my "apparently" is based on watching that.

Also, constructor resolution is a somewhat special matter, but I'll elaborate in #401.

Well, at least this means we can go ahead with a straight forward implementation of MRO, and get these details correct at the very end, if at all.