getattr-demo.py

>>> class Dog:
...     def __init__(self, breed, color):
...         self.breed = breed
...         self.color = color
...
>>> dog1 = Dog("bulldog", "brown")
>>>
>>> dog1
<__main__.Dog object at 0x7fe114d36580>
>>> dog1.attr
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Dog' object has no attribute 'attr'
>>> getattr(dog1, "breed")
'bulldog'
>>> getattr(dog1, "attr")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Dog' object has no attribute 'attr'
>>> getattr(dog1, "attr", "default_value")
'default_value'