Python import precedence: packages or modules?

TLDR; a package takes precedence over a module of the same name if they are in the same directory.

From the docs:

"When a module named spam is imported, the interpreter searches for a file named spam.py in the current directory, and then in the list of directories specified by the environment variable PYTHONPATH. This has the same syntax as the shell variable PATH, that is, a list of directory names."

This is a bit misleading because the interpreter will also look for a package called spam (a directory called spam containing an __init__.py file). Since the directory entries are sorted before searching, packages take precedence over modules with the same name if they are in the same directory because spam comes before spam.py.

Note that "current directory" is relative to the main script path (the one where __name__ == '__main__' is True). So if you are at /home/billg calling /foo/bar.py, "current directory" refers to /foo.

Packages (directories with __init__.py) take precedence over modules. The documentation of this fact is difficult to find but you can see this in the source: python 2.7, python 3.6 (thanks @qff for the find).

You will also need a __init__.py within the foo directory for your example to work.

If other.py is inside of foo/ then it will load foo.py (not the directory foo/) because it will look in the current directory first (unless you've played with PYTHONPATH or sys.path).

I would like to complement the accepted answer. For Python 3.3+, namespace packages have been introduced and the import order according to PEP 420 follows:

During import processing, the import machinery will continue to iterate over each directory in the parent path as it does in Python 3.2. 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.

from a python shell:

from foo import bar

print bar.__file__

should tell you which file has been imported

Rob