8.4.2 Intra-package References

The submodules often need to refer to each other. For example, the ‘surround’ module might use the echo module. In fact, such references are so common that the import statement first looks in the containing package before looking in the standard module search path. Thus, the surround module can simply use import echo or from echo import echofilter. If the imported module is not found in the current package (the package of which the current module is a submodule), the import statement looks for a top-level module with the given name.

When packages are structured into subpackages (as with the ‘Sound’ package in the example), there's no shortcut to refer to submodules of sibling packages - the full name of the subpackage must be used. For example, if the module ‘Sound.Filters.vocoder’ needs to use the echo module in the ‘Sound.Effects’ package, it can use from Sound.Effects import echo.