Why less emphasis on private data?

[Chris Mellon]

Private data in the C++ and Java OO worlds is so taught so much and
emphasized so often that people have started thinking of it as being
desirable for its own sake. But the primary motivation for it grew out
of the need to maintain compatible interfaces. These languages rely on
a great deal of shared information between provides and clients of
interfaces in order to work correctly - public/private interfaces are
simply a reflection of that requirement (and the fact that your
clients still need to see the stuff you declare as private is an
example of a leak in that abstraction).

Python doesn't have these problems, so the only use for private
information is to warn your clients away from access to certain names.
There's no need for compiler enforcement of that, as a convention is
just as effective.

The remaining arguments are generally outgrowths of "but my code is
SECRET", which just isn't true in general, even less true of Python,
and not really a healthy attitude anyway.