以下摘自关于self的Python文档:

As in Modula-3, there are no shorthands [in Python] for referencing the object’s members from its methods: the method function is declared with an explicit first argument representing the object, which is provided implicitly by the call. Often, the first argument of a method is called self. This is nothing more than a convention: the name self has absolutely no special meaning to Python. Note, however, that by not following the convention your code may be less readable to other Python programmers, and it is also conceivable that a class browser program might be written that relies upon such a convention.

有关更多信息，请参阅Python类文档教程。

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)。

假设你有一个类ClassA，它包含一个方法methodA，定义为:

def methodA(self, arg1, arg2):
    # do something

objectA是这个类的一个实例。

现在当objectA。当调用methodA(arg1, arg2)时，python会在内部将其转换为:

ClassA.methodA(objectA, arg1, arg2)

self变量引用对象本身。

当对象实例化时，对象本身被传递到self参数中。

因此，对象的数据被绑定到对象上。下面是一个示例，说明您可能希望如何可视化每个对象的数据。注意“self”是如何被对象名称替换的。我并不是说下面这个示例图是完全准确的，但希望它能在可视化self的使用方面起到一定的作用。

对象被传递到self参数中，这样对象就可以保存自己的数据。

Although this may not be wholly accurate, think of the process of instantiating an object like this: When an object is made it uses the class as a template for its own data and methods. Without passing it's own name into the self parameter, the attributes and methods in the class would remain as a general template and would not be referenced to (belong to) the object. So by passing the object's name into the self parameter it means that if 100 objects are instantiated from the one class, they can all keep track of their own data and methods.

如下图所示:

“self”这个词指的是一个类的实例

class foo:
      def __init__(self, num1, num2):
             self.n1 = num1 #now in this it will make the perimeter num1 and num2 access across the whole class
             self.n2 = num2
      def add(self):
             return self.n1 + self.n2 # if we had not written self then if would throw an error that n1 and n2 is not defined and we have to include self in the function's perimeter to access it's variables

"self"关键字保存类的引用，这取决于你是否想要使用它，但如果你注意到，每当你在python中创建一个新方法时，python会自动为你写self关键字。如果你做了一些研究，你会注意到，如果你在一个类中创建了两个方法，并试图在另一个方法中调用一个方法，它不会识别方法，除非你添加self(类的引用)。

class testA:
def __init__(self):
    print('ads')
def m1(self):
    print('method 1')
    self.m2()
def m2(self):
    print('method 2')

以下代码抛出无法解决的引用错误。

class testA:
def __init__(self):
    print('ads')
def m1(self):
    print('method 1')
    m2()  #throws unresolvable reference error as class does not know if m2 exist in class scope
def m2(self):
    print('method 2')

现在让我们看看下面的例子

class testA:
def __init__(self):
    print('ads')
def m1(self):
    print('method 1')
def m2():
    print('method 2')

现在，当您创建类testA的对象时，您可以像这样使用类对象调用方法m1()，因为方法m1()包含了self关键字

obj = testA()
obj.m1()

但是如果你想调用方法m2()，因为它没有自我引用，所以你可以像下面这样直接使用类名调用m2()

testA.m2()

但是要坚持使用self关键字，因为它还有其他好处，比如在内部创建全局变量等等。