Some Thoughts on Python caused by _ dict _ and dir (), python _ dict _

Some Thoughts on Python caused by _ dict _ and dir (), python _ dict _

For the differences and functions between _ dict _ and dir (), refer to this article:

Differences between Python _ dict _ and dir ()

Let's talk about the problems I encountered:

class Demo:  def __init__(self, name, age):    self.name = name    self.age = age  def func(self):    print('Hello {0}'.format(self.name))>>> d1 = Demo('Pythoner', 24)>>> hasattr(d1, 'func')True>>> d1.__dict__{'age': 24, 'name': 'Pythoner'}>>dir(d1)[ 'age', 'func', 'name','__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']

First, we know that the instance method can also be regarded as an attribute and can be verified through the hasattr () function. _ dict _ is a dictionary used to store object attributes, but its return value does not contain 'function '!

Looking at the dir () function, it will automatically find all the attributes of an object (including attributes inherited from the parent class), and its return value contains 'func '.

Therefore, I guess that the "instance method" does not belong to the "private" attribute of the instance, but is shared by all instances of this class!

An instance requires a "private" process to obtain private properties, just like the _ init _ initialization function!

Verification:

class Demo2:  def __init__(self, name):    self.name = name  def func(self):    print('----get arg country----')    self.country = 'China'>>> d2 = Demo2('Pythoner')>>> d2.__dict__{'name': 'Pythoner'}>>> d2.func()----get arg country---->>> d2.__dict__{'country': 'China', 'name': 'Pythoner'}

The reason why "instance method" is called an instance method, or when each instance executes an instance method, different results are generated for different private attributes.SelfParameters.

When an instance executes an instance method, it searches for the method in the class to which it belongs, and thenSelfThe parameter passes the instance itself in, and the private attributes of the instance are passed together.SelfThe instance and method are bound.

Summary

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