What's the purpose of “import package”?

Question

As I just found out import package does not make the package's modules available through package.module. The same obviously holds true for from package import subpackage as well as from package import *

What's the purpose of importing a package at all then if I can't access its submodules but only the objects defined in __init__.py ?

It makes sense to me that from package import * would bloat the namespace, which, however, doesn't apply in case of the other two ways! I also understand that loading all submodules might take a long time . But I don't know what these unwanted side-effects, "that should only happen when the sub-module is explicitly imported", are which the author of the previous link mentions. To me it looks like doing an import package[.subpackage] (or from package import subpackage ) makes absolutely no sense if I don't exactly want to access objects provided in __init__.py .

Are those unwanted side effects really that serious that the language actually has to protect the programmer from causing them? Actually, I thought that Python was a little bit more about "If the programmer wants to do it, let him do it." In my case, I really do want to import all submodules with the single statement from package import subpackage , because I need all of them! Telling Python in the __init__.py file which submodules I'm exactly talking about (all of them!) is quite cumbersome from my point of view.

Please enlighten me. :)

Answer 1

It's up to the package if it automatically imports submodules in its __init__.py or not. For example os automatically imports os.path , so this works:

import os
print os.path.abspath('somefile')

So the creator of the package can decide what is best. If automatically loading all submodules would take a rather long time and would rarely be needed, it probably shouldn't be done. If all the submodules are always required they probably should be imported automatically.

If you think a package imports not enough you could work around it by writing your own wrapper module that does all the imports, and then use that with from wrappermodule import * .

Answer 2

As said, the solution is to import each submodule. You can use a hack to avoid listing them:

__init__.py

import os

def import_sub():
  for fn in os.listdir(os.path.dirname(__file__)):
    if fn.endswith(".py") and fn != "__init__.py":
      __import__(".".join([__name__, os.path.basename(fn)[:-3]]), level=0)
import_sub()
del import_sub  # if desired

This will easily break under some circumstances. However, it will handle the common case and could be temporarily suitable.