with no known parent package.
Previously SystemError was raised if the parent package didn't exist
(e.g., __package__ was set to '').
Thanks to Florent Xicluna and Yongzhi Pan for reporting the issue.
In a previous change, __spec__.parent was prioritized over
__package__. That is a backwards-compatibility break, but we do
eventually want __spec__ to be the ground truth for module details. So
this change reverts the change in semantics and instead raises an
ImportWarning when __package__ != __spec__.parent to give people time
to adjust to using spec objects.
not defined for a relative import.
This is the start of work to try and clean up import semantics to rely
more on a module's spec than on the myriad attributes that get set on
a module. Thanks to Rose Ames for the patch.
importlib.abc.Loader.exec_module() is also defined.
Before this change, create_module() was optional **and** could return
None to trigger default semantics. This change now reduces the
options for choosing default semantics to one and in the most
backporting-friendly way (define create_module() to return None).
Adds `load_package_tests` function to test.support, uses it in test_asyncio,
test_email, test_json, test_tools, test_importlib and all test_importlib
sub-packages to implement test discovery.
and stop importlib.machinery.FileFinder treating '' as '.'.
Previous PathFinder transformed '' into '.' which led to __file__ for
modules imported from the cwd to always be relative paths. This meant
the values of the attribute were wrong as soon as the cwd changed.
This change now means that as long as the site module is run (which
makes all entries in sys.path absolute) then all values for __file__
will also be absolute unless it's for __main__ when specified by file
path in a relative way (modules imported by runpy will have an
absolute path).
Now that PathFinder is no longer treating '' as '.' it only makes
sense for FileFinder to stop doing so as well. Now no transformation
is performed for the directory given to the __init__ method.
Thanks to Madison May for the initial patch.
To make sure there is no issue with code that is both Python 2 and 3
compatible, there are no plans to remove the module any sooner than
Python 4 (unless the community moves to Python 3 solidly before then).
ImportError.
The exception is raised by import when a module could not be found.
Technically this is defined as no viable loader could be found for the
specified module. This includes ``from ... import`` statements so that
the module usage is consistent for all situations where import
couldn't find what was requested.
This should allow for the common idiom of::
try:
import something
except ImportError:
pass
to be updated to using ModuleNotFoundError and not accidentally mask
ImportError messages that should propagate (e.g. issues with a
loader).
This work was driven by the fact that the ``from ... import``
statement needed to be able to tell the difference between an
ImportError that simply couldn't find a module (and thus silence the
exception so that ceval can raise it) and an ImportError that
represented an actual problem.
Serhiy Storchaka
Ville Skyttä
Eric Snow
Brett Cannon
Berker Peksag
Zachary Ware
Barry Warsaw