How to import a module in Python with importlib.im

问题:

I'm trying to use importlib.import_module in Python 2.7.2 and run into the strange error.

Consider the following dir structure:

    a
    |
    + - __init__.py
      - b
        |
        + - __init__.py
          - c.py

a/b/__init__.py has the following code:

    import importlib

    mod = importlib.import_module("c")

(In real code "c"has a name.)

Trying to import a.b, yields the following error:

    >>> import a.b
    Traceback (most recent call last):
      File "", line 1, in 
      File "a/b/__init__.py", line 3, in 
        mod = importlib.import_module("c")
      File "/opt/Python-2.7.2/lib/python2.7/importlib/__init__.py", line 37, in   import_module
        __import__(name)
    ImportError: No module named c

What am I missing?

Thanks!

回答1:

For relative imports you have to:

• a) use relative name

• b) provide anchor explicitly

  importlib.import_module('.c', 'a.b')
  

Of course, you could also just do absolute import instead:

importlib.import_module('a.b.c')

回答2:

I think it's better to use importlib.import_module('.c', __name__) since you don't need to know about a and b.

I'm also wondering that, if you have to use importlib.import_module('a.b.c'), why not just use import a.b.c?

回答3:

And don't forget to create a __init__.py with each folder/subfolder (even if they are empty)