The reason you need to use self. is because Python does not use special syntax to refer to instance attributes. Python decided to do methods in a way that makes the instance to which the method belongs be passed automatically, but not received automatically: the first parameter of methods is the instance the method is called on. That makes methods entirely the same as functions, and leaves the actual name to use up to you (although self is the convention, and people will generally frown at you when you use something else.) self is not special to the code, it's just another object.

Python could have done something else to distinguish normal names from attributes -- special syntax like Ruby has, or requiring declarations like C++ and Java do, or perhaps something yet more different -- but it didn't. Python's all for making things explicit, making it obvious what's what, and although it doesn't do it entirely everywhere, it does do it for instance attributes. That's why assigning to an instance attribute needs to know what instance to assign to, and that's why it needs self..

与前面提到的所有其他原因一样，它允许更容易地访问被覆盖的方法;你可以调用Class.some_method(inst)。

举个例子说明它的用处:

class C1(object):
    def __init__(self):
         print "C1 init"

class C2(C1):
    def __init__(self): #overrides C1.__init__
        print "C2 init"
        C1.__init__(self) #but we still want C1 to init the class too

>>> C2()
"C2 init"
"C1 init"

自我是不可避免的。

问题是，self是隐式的还是显式的。 Guido van Rossum解决了这个问题说self必须留下来。

那么自我生活在哪里呢?

如果我们坚持函数式编程，我们就不需要self了。 一旦我们进入Python OOP，我们就会发现自己在那里。

下面是带有方法m1的典型用例类C

class C:
    def m1(self, arg):
        print(self, ' inside')
        pass

ci =C()
print(ci, ' outside')
ci.m1(None)
print(hex(id(ci))) # hex memory address

这个程序将输出:

<__main__.C object at 0x000002B9D79C6CC0>  outside
<__main__.C object at 0x000002B9D79C6CC0>  inside
0x2b9d79c6cc0

self保存类实例的内存地址。 self的目的是保存实例方法的引用，并使我们能够显式地访问该引用。

注意有三种不同类型的类方法:

静态方法(读作:函数)， 类方法, 实例方法(已提到)。

Self的作用类似于当前对象名或类的实例。

# Self explanation.


 class classname(object):

    def __init__(self,name):

        self.name=name
        # Self is acting as a replacement of object name.
        #self.name=object1.name

   def display(self):
      print("Name of the person is :",self.name)
      print("object name:",object1.name)


 object1=classname("Bucky")
 object2=classname("ford")

 object1.display()
 object2.display()

###### Output 
Name of the person is : Bucky
object name: Bucky
Name of the person is : ford
object name: Bucky

从医生那里，

方法的特殊之处在于实例对象是作为函数的第一个参数传递的。在我们的例子中，调用x.f()完全等价于MyClass.f(x)。一般来说，调用带有n个参数列表的方法相当于调用带有参数列表的相应函数，该参数列表是通过在第一个参数之前插入方法的实例对象创建的。

在此之前的相关片段，

class MyClass:
    """A simple example class"""
    i = 12345

    def f(self):
        return 'hello world'

x = 我的类（）

Self是对对象本身的引用，因此，它们是相同的。 Python方法不是在对象本身的上下文中调用的。 self在Python中可以用来处理自定义对象模型或其他东西。