python - order of import for modules

Question

For example there is some folder:

.
├── file_a.py
├── file_b
│   └── __init__.py
└── file_b.py

where file_a.py has something like:

from file_b import some_function

I know this is definitely not good practice, but what is the order of resolution behind?

i.e. How python decides which module to be imported for an "absolute import"?

Answer 1

I'm not sure where (or whether) this information is in the documentation - a quick check in the import system docs didn't turn it up - but PEP 420 says the following:

While looking for a module or package named "foo", for each directory in the parent path:

• If <directory>/foo/__init__.py is found, a regular package is imported and returned.
• If not, but <directory>/foo.{py,pyc,so,pyd} is found, a module is imported and returned. The exact list of extension varies by platform and whether the -O flag is specified. The list here is representative.
• If not, but <directory>/foo is found and is a directory, it is recorded and the scan continues with the next directory in the parent path.
• Otherwise the scan continues with the next directory in the parent path.

If the scan completes without returning a module or package, and at least one directory was recorded, then a namespace package is created.

So according to PEP 420, if a package and a non-package module are found in the same directory with the same name, the package wins.

Answer 2

Based on @JonKiparsky 's suggestion, I dug through importlib a bit, and finally found importlib._bootstrap.FileFinder.find_spec, which does indeed explicitly check for a directory before looking for valid files that fit the package name. Glad to see @user2357112 's answer, though, that this is supposed to be defined behavior, and isn't just happenstance.