EDIT: There are better/more coherent answers to this question in other questions:
Why doesn’t it work? It’s because python doesn’t record where a package was loaded from. So when you do python -m test_A.test
, it basically just discards the knowledge that test_A.test
is actually stored in package
(i.e. package
is not considered a package). Attempting from ..A import foo
is trying to access information it doesn’t have any more (i.e. sibling directories of a loaded location). It’s conceptually similar to allowing from ..os import path
in a file in math
. This would be bad because you want the packages to be distinct. If they need to use something from another package, then they should refer to them globally with from os import path
and let python work out where that is with $PATH
and $PYTHONPATH
.
When you use python -m package.test_A.test
, then using from ..A import foo
resolves just fine because it kept track of what’s in package
and you’re just accessing a child directory of a loaded location.
Why doesn’t python consider the current working directory to be a package? NO CLUE, but gosh it would be useful.