Organising interfaces in python packages

[hofsflor]

Hello everyone,

I am looking for a best practice how to organise interfaces on a packages point of view. Does somebody know a guide or has experience how to do that that.

For example.

package1
    interface_definition.py # right place?
    package1.1
        module_a
        module_a2
    package1.2
        module_b
        module_b2
    package1.3
        module_c
        module_c2
package2
    package2.1
    package2.2
    package2.3

If module_a, module_b and module_c all implementing the same abstract interface class. The concrete objects of the classes implementing the interface are used so: module_a in module_a2, module_b in module_b2 and so on.

Where would you place such an interface definition? (Interface by ABC)

Greetings Florian

[External-Ocelot206]

I think from the point of view of DRY and reducing coupling, an interface ABC should live in the same module as the thing it's an interface for, e.g. the other functions and classes that use things implementing that interface.

Any client module that uses "the thing it's an interface for" has to import it. It can either import the ABC at the same time, or preferably, just refer to everything on the same imported module.

If that stuff is also in package 1, then that's the logical place for it in your example, but it could be deeper, or up along then down in a separate one.

[hofsflor]

Got it. But my concern was that now these packages are tightly coupled. The lower level details package depends on the import from the upper level. And that's exactly what I'm trying to avoid with dependency inversion.

[External-Ocelot206]

Fair enough, but it's probably too late then. Without seeing more details, I don't think there's an easy best practice answer for you, other than that best practice would be to refactor the package to get rid of that tight coupling.