Based on Python-ideas thread My objections to implicit package directories by Nick Coghlan and this message from Yuval Greenfield:
I've always had trouble understanding and explaining the complexities and intricacies of python packaging.` Is there a most basic but comprehensive list of use cases?
- standard library
- import from a list of paths to be searched.
- current project
- import from a relative path based on this file's current directory
- package bundled with project
- import from a relative path based on an anchor directory
- virtual-env
- import from an alternative lists of paths based on an anchor directory