Python-从包中导入所有类时是否可以导入特定类

Question

I have a package set up with a tree structure like

pkg\  
    __init__.py  
    module1.py  
        Class11  
        Class12  
    module2.py  
        Class21  
        function21  

I want specific classes and functions to be in the global namespace such that when I start my script with

from pkg import *

I will be able to directly use, say, Class11, Class12, and function21. Is this possible? The motivation behind it is to allow for quick and light usages in small scripts or interactive mode. It's implicitly known that with longer scripts one would not use import all and traverse the package structure properly.

EDIT: I could import Class11, Class12, and function21 in pkg's __init__.py , but in this way, when I do the regular import pkg I will still be able to access Class11 by pkg.Class11 instead of the proper pkg.module1.Class11 . Preferably I want pkg.module1.Class11 to be the only way if I'm not doing import * .

Answer 1

Sure. The * means "everything". ^* If you don't want everything, but instead want a specific list of names, just use those names:

from pkg import Class11, Class21, function21

---

Of course this assumes that pkg already imports those names from its submodules. But if that weren't true, your * import wouldn't work either.

If that isn't true, but you want to know how to make it true, you just do something similar in pkg/__init__.py :

from .module1 import Class11, Class12
from .module2 import Class21, function21

Or, maybe:

from .module1 import __all__ as _all1
from .module2 import __all__ as _all2
from .module1 import *
from .module2 import *

__all__ = _all1 + _all2

---

_{* Well, not quite "everything". If there's an __all__ , it means "every name in __all__ "; if not, it means "every name that doesn't start with _ ". But close enough for our purposes.}

Answer 2

Yes, you can. See what Flask did here :

Basically, you can import the functions and classes in __init__.py like this:

from .app import Flask, Request, Response
from .config import Config

Now we can do:

from Flask import Flask ,Request

Answer 3

Set up your __init__.py like this:

from .module1 import Class11, Class12
from .module2 import Class21, function21