How to Fix the Microsoft Visual Studio Error: Package Did Not Load Correctly

To elaborate on Ignacio Vazquez-Abrams's answer:

The Python import mechanism works relative to the __name__ of the current file. When you execute a file directly, it doesn't have its usual name, but has "__main__" as its name instead. So relative imports don't work.

You can, as Igancio suggested, execute it using the -m option. If you have a part of your package that is meant to be run as a script, you can also use the __package__ attribute to tell that file what name it's supposed to have in the package hierarchy.

See http://www.python.org/dev/peps/pep-0366/ for details.

I started to see this on a fresh Windows and Visual Studio 2013 Ultimate with Update 2 installation (although others have also reported it on Updates 3 and 4, as well as the Professional version).

To resolve the problem, close all Visual Studio instances, then delete all files in the following folder:

Visual Studio 2013

%localappdata%\Microsoft\VisualStudio\12.0\ComponentModelCache

It worked fine for me. Thanks to this article.

Visual Studio 2015

%localappdata%\Microsoft\VisualStudio\14.0\ComponentModelCache

Visual Studio 2017

%localappdata%\Microsoft\VisualStudio\15.0_xxxx\ComponentModelCache

Visual Studio 2019

%localappdata%\Microsoft\VisualStudio\16_xxxx\ComponentModelCache