Python Import – Order of Import for Modules Explained

pythonpython-import

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"?

Best Answer

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.

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