How to import a module in Python with importlib.import_module

Question

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!

score 126 · Accepted Answer · edited Dec 07 '18 at 07:04

126

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')

edited Dec 07 '18 at 07:04

answered May 20 '12 at 16:17

Cat Plus Plus

119,938
26
191
218

This works for python 3.x, too. (OP asked about 2.7.) – JimB May 24 '22 at 15:45

score 41 · Answer 2 · answered Jul 08 '15 at 07:03

41

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?

answered Jul 08 '15 at 07:03

Gerald

849
1
7
17

40

It's useful when module name is a variable. – Bhargav Nanekalva Nov 01 '15 at 09:45
3

It's also useful when the module name is not a valid python identifier (e.g. has dashes in it). – fool4jesus Feb 28 '20 at 17:36

score 22 · Answer 3 · answered Jun 21 '17 at 09:52

22

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

answered Jun 21 '17 at 09:52

H.Sechier

251
2
7

3

Why though? I found this: https://stackoverflow.com/questions/448271/what-is-init-py-for#448279 with the comment by @TwoBItAlchemist being most useful I think """Python searches a list of directories to resolve names in, e.g., import statements. Because these can be any directory, and arbitrary ones can be added by the end user, the developers have to worry about directories that happen to share a name with a valid Python module, such as 'string' in the docs example. To alleviate this, it ignores directories which do not contain a file named _ _ init _ _.py (no spaces), even if it is blank.""" – Goblinhack May 29 '20 at 17:55

How to import a module in Python with importlib.import_module

3 Answers3

Linked

Related