Importing files in Python from __init__.py

问题:

Suppose I have the following structure:

app/
  __init__.py
  foo/
    a.py
    b.py
    c.py
    __init__.py

a.py, b.py and c.py share some common imports (logging, os, re, etc). Is it possible to import these three or four common modules from the __init__.py file so I don't have to import them in every one of the files?

Edit: My goal is to avoid having to import 5-6 modules in each file and it's not related to performance reasons.

回答1:

No, they have to be put in each module's namespace, so you have to import them somehow (unless you pass logging around as a function argument, which would be a weird way to do things, to say the least).

But the modules are only imported once anyway (and then put into the a, b, and c namespaces), so don't worry about using too much memory or something like that.

You can of course put them into a separate module and import that into each a, b, and c, but this separate module would still have to be imported everytime.

回答2:

You can do this using a common file such as include.py, but it goes against recommended practices because it involves a wildcard import. Consider the following files:

app/
    __init__.py
foo/
    a.py
    b.py
    c.py
    include.py <- put the includes here.
    __init__.py

Now, in a.py, etc., do:

from include import *

As stated above, it's not recommended because wildcard-imports are discouraged.

回答3:

Yes, but don't do it. Seriously, don't. But if you still want to know how to do it, it'd look like this:

import __init__

re = __init__.re
logging = __init__.logging
os = __init__.os

I say not to do it not only because it's messy and pointless, but also because your package isn't really supposed to use __init__.py like that. It's package initialization code.