Python Learning note 7 (Class/Object properties)

27. Properties of the __DICT__ System 1) object may come from:

• The definition of its class, called the Class attribute
• Inherit the definition of the parent class
• The object instance definition (assigned value when initializing the object), called the object property

2) The properties of the object are stored in the object's __dict__In the properties:

• __dict__ is a dictionary, the key is the property name, and the value is the property itself.

Example:

Class Bird (object):    feather = True         # parent Class Class chicken (bird):    fly = False    def __init__ (self, age ):        Self.age = Age     # subclass Summer = Chicken (2)        # Subclass of Object Print (bird.__dict__)       # Parent Class Property

{' __dict__ ': <attribute ' __dict__ ' of ' bird ' objects>,   ' __module__ ': ' __main__ ',   ' __weakref__ ': < Attribute ' __weakref__ ' of ' bird ' objects>,   'feather': True, ' __doc__ ': None}

Print (chicken.__dict__)    # sub-class properties

{'fly': False, ' __module__ ': ' __main__ ', ' __doc__ ': None, '__init__': <function __init__ at 0x2b91db476d70>}

Print (summer.__dict__)     #对象属性

{'age ': 2}

3) The attributes are defined hierarchically:

For example, the above is divided into Object/bird/chicken/summer four layers.

When we need to invoke a property, Python walks up one layer at a time until the nearest property is found.

__class__ and __base__

The __class__ property can help the object to query its class;

The __base__ property can query its parent class through these class

4) Modify/reference the properties of the object

The following two ways are equivalent to each other:

Summer.__dict__[' age '] = 3       print (summer.__dict__[' age ')

Summer.age = 3                   print (summer.age)

28.

Python Learning note 7 (Class/Object properties)