Private Variables and Class-local References

Imagine you have a class with a private member:

class Foo:
    __attr= 5

Inside the class, this attribute can be referenced as __attr:

class Foo:
    __attr= 5
    print(__attr) # prints 5

But not outside of the class:

print(Foo.__attr) # raises AttributeError

But it's different if you use eval, exec, or execfile inside the class:

class Foo:
    __attr= 5

    print(__attr) # prints 5
    exec 'print(__attr)' # raises NameError

This is explained by the paragraph you quoted. exec does not consider Foo to be the "current class", so the private attribute cannot be referenced (unless you reference it as Foo._Foo__attr).