[ Python 常見問題 ] Dynamic creation from string name of a class in dynamically imported module?

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Question
In python, I have to instantiate certain class, knowing its name in a string, but this class 'lives' in a dynamically imported module. How to do it?

HowTo
You can use getattr to access the attributes of loaded module. Consider you have module below:
- my_mod.py

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1. class MyClass:  
2.     def __init__(self, name, age):  
3.         self.name = name  
4.         self.age = age  
5.   
6.     def __str__(self):  
7.         return f"My name is {self.name} and my age is {self.age}"  

The default way to use this module:

>>> from my_mod import *
>>> john = MyClass('John', 40)
>>> print(john)
My name is John and my age is 40

To access the module my_mod and create object of class MyClass dynamically:

>>> my_mod = __import__('my_mod')
>>> my_clz = getattr(my_mod, 'MyClass')
>>> john = my_clz('John', 40)
>>> print(john)
My name is John and my age is 40

Or you can leverage another package importlib:

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1. import importlib  
2. module = importlib.import_module(module_name)  
3. class_ = getattr(module, class_name)  
4. instance = class_()