#17115,17116: Have modules initialize the __package__ and __loader__

attributes to None.

The long-term goal is for people to be able to rely on these
attributes existing and checking for None to see if they have been
set. Since import itself sets these attributes when a loader does not
the only instances when the attributes are None are from someone
overloading __import__() and not using a loader or someone creating a
module from scratch.

This patch also unifies module initialization. Before you could have
different attributes with default values depending on how the module
object was created. Now the only way to not get the same default set
of attributes is to circumvent initialization by calling
ModuleType.__new__() directly.

1 files changed, 5 insertions, 0 deletions

diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
index ca515f6..9774241 100644
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -231,3 +231,8 @@ that may require changes to your code.
   :exc:`NotImplementedError` blindly. This will only affect code calling
   :func:`super` and falling through all the way to the ABCs. For compatibility,
   catch both :exc:`NotImplementedError` or the appropriate exception as needed.
+
+* The module type now initializes the :attr:`__package__` and :attr:`__loader__`
+  attributes to ``None`` by default. To determine if these attributes were set
+  in a backwards-compatible fashion, use e.g.
+  ``getattr(module, '__loader__', None) is not None``.
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