Attribute Access

Describing Attribute Access

• The following class methods can be used for attribute access:

  • __getattribute__()
  • __getattr__()
  • __setattr__()
  • __delattr__()

• __getattribute__() has the following properties:

  • Invoked before looking at the actual attributes on the object
  • As a result, it can be tricky to implement correctly

• __getattr__() has the following properties:

  • Invoked if the attribute wasn't found
  • It's good for implementing a fallback for missing attributes

• __setattr__() has the following properties:

  • Invoked when setting an attribute

• __delattr__() has the following properties:

  • Invoked when deleting an attribute
• In most scenarios, we'll prefer __getattr__() over __getattribute__()
• We would most likely either implement __getattribute__() or __getattr__(), but not both
• These special methods are used to parameterize access to attributes

>>> class Person:
...     def __init__(self, name, age, sex):
...         self.name = name
...         self.age = age
...         self.sex = sex

>>> attrs = ['name', 'age']
>>> p = Person('Jeff', 25, 'm')
>>> [getattr(p, a) for a in attrs]
['Jeff', 25]

Summarizing Special Methods

References

• Python Essential Reference
• Use-Cases of getattr and getattribute
• Why use These Special Methods?