Polymorphic imports

[Travis Griggs]

I guess this is kind of like mocking for testing. I have a simple module that's imported in a number of other spots in my program. There's a condition in the OS/filesystem where I'd like to import a polymorphically compatible variant of the same module. Can this be accomplished in a sort of once-and-only once spot?

For example, consider something like this:

client/
  module_a
  module_a_prime
lib/
  paths
   lib_a
   lib_b
   ...
model/
  model_a
  model_b
  ...
top_level_a
top_level_b
...


I have a number of imports of module_a. I have a paths module that isolates all of my file system access, and that's where the determination can be made which one to use, so I tried to do something like:

def dynamic_client_module():
   return client.module_a_prime if the_condition_occurs else client.module_a


Hoping that I could do something like

from lib import paths
import paths.dynamic_client_module()

But this seems to not work. Import can only take real modules? Not programatic ones?

Is there a Not-Too-Evil-Way(tm) to add a level of programmatic indirection in the import declarations? Or some other trick from a different angle?