``sys.path`` looking for the package subdirectory.
The :file:`__init__.py` files are required to make Python treat directories
-containing the file as packages. This prevents directories with a common name,
+containing the file as packages (unless using a :term:`namespace package`, a
+relatively advanced feature). This prevents directories with a common name,
such as ``string``, from unintentionally hiding valid modules that occur later
on the module search path. In the simplest case, :file:`__init__.py` can just be
an empty file, but it can also execute initialization code for the package or