[ Python 常見問題 ] import module from string variable

Source From Here 
Question 
Problem is that I can't find a way to instruct Python to load submodule from string. 

How-To 
The __import__ function can be a bit hard to understand. In Python 2.7 and Python 3.1 or later, you can use importlib. Supposed you have one module: 
- test.py 

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1. def add(a, b):  
2.     return a + b  
3.   
4. def sub(a, b):  
5.     return a - b  
6.   
7.   
8. class Clz:  
9.     def __init__(self, name):  
10.         self.name = name  
11.   
12.     def __repr__(self):  
13.         return self.__str__(self)  
14.   
15.     def __str__(self):  
16.         return "Name={}".format(self.name)  

Then you can import it his way: 

>>> import importlib 
>>> modu_name = 'test' 
>>> modu = importlib.import_module(modu_name) 
>>> modu.add(1, 2) 
3 
>>> modu.sub(2, 1) 
1 
>>> obj = modu.Clz('john') 
>>> print(obj) 
Name=john

Some notes: 

* If you're trying to import something from a sub-folder e.g. ./feature/email.py, the code will look like importlib.import_module("feature.email") 
* You can't import anything if there is no __init__.py in the folder with file you are trying to