我认为这和PEP 227有关

Names in class scope are not accessible. Names are resolved in the innermost enclosing function scope. If a class definition occurs in a chain of nested scopes, the resolution process skips class definitions. This rule prevents odd interactions between class attributes and local variable access. If a name binding operation occurs in a class definition, it creates an attribute on the resulting class object. To access this variable in a method, or in a function nested within a method, an attribute reference must be used, either via self or via the class name.

我认为这和PEP 227有关

Names in class scope are not accessible. Names are resolved in the innermost enclosing function scope. If a class definition occurs in a chain of nested scopes, the resolution process skips class definitions. This rule prevents odd interactions between class attributes and local variable access. If a name binding operation occurs in a class definition, it creates an attribute on the resulting class object. To access this variable in a method, or in a function nested within a method, an attribute reference must be used, either via self or via the class name.

我建议大家应该读读Guido van Rossum关于这个话题的博客——为什么外显的自我必须留下来。

When a method definition is decorated, we don't know whether to automatically give it a 'self' parameter or not: the decorator could turn the function into a static method (which has no 'self'), or a class method (which has a funny kind of self that refers to a class instead of an instance), or it could do something completely different (it's trivial to write a decorator that implements '@classmethod' or '@staticmethod' in pure Python). There's no way without knowing what the decorator does whether to endow the method being defined with an implicit 'self' argument or not. I reject hacks like special-casing '@classmethod' and '@staticmethod'.

这是为了最小化方法和函数之间的差异。它允许您轻松地在元类中生成方法，或在运行时向已存在的类添加方法。

e.g.

>>> class C:
...     def foo(self):
...         print("Hi!")
...
>>>
>>> def bar(self):
...     print("Bork bork bork!")
...
>>>
>>> c = C()
>>> C.bar = bar
>>> c.bar()
Bork bork bork!
>>> c.foo()
Hi!
>>>

它还(据我所知)使python运行时的实现更容易。

Python不会强制你使用"self"。你可以给它起任何你想要的名字。你只需要记住方法定义头中的第一个参数是对对象的引用。

self形参保存当前调用对象。

class class_name:
    class_variable
    def method_name(self,arg):
        self.var=arg 
obj=class_name()
obj.method_name()

在这里，self参数保存对象obj。因此，语句self。Var表示obj.var