PEP366 states:

The major proposed change is the introduction of a new module level attribute, __package__. When it is present, relative imports will be based on this attribute rather than the module name attribute.

Will it ever be the case that it is not present? I know it can be None, '', or __name__.rpartition('.')[0] but, will it ever be that referencing __package__ will throw me an attribute not found error? Is it safe to say that __package__ is always present actually?