1. Nested function ( Internal function )
Under what circumstances do you usually use nested functions ？
1）. encapsulation - Data hiding cannot be accessed externally “ Nested function ”.
2）. implement DRY(Don’tRepeatYourself) Principle nested function , Let's avoid duplicate code inside the function .
3）. Closure
2.nonlocal keyword
nonlocal Local variables used to declare the outer layer .global Used to declare global variables .
3.LEGB The rules
Python Looking for “ name ” when , Is in accordance with the LEGB Rule lookup ：Local-->Enclosed-->Global-->Builtin
Local It refers to the method interior of a function or class
Enclosed Refers to nested functions （ One function encapsulates another , Closure ）
Global It refers to the global variables in the module
Built in refer to Python A special name reserved for yourself .
4. object-oriented
notes ：Python Support process oriented 、 object-oriented 、 Functional programming and other programming paradigms .
4.1 object
Put different types of data 、 Method （ It's a function ） Put it together , It's the object
4.2 The definition of a class
We define the properties of data types through classes （ data ） And methods （ Behavior ）, in other words ,“ Class packages behavior and state together ”.
An object is a concrete entity of a class , Commonly referred to as “ Class ”. Class as “ Cookie Mold ”, The object is based on this “ The mould ” Made “ cookies ”.
Python in ,“ Everything is the object ”. Class is also called “ Class object ”, An instance of a class is also called “ Instance object ”.
4.2.1 The syntax format of the definition class is as follows ：
class Class name ：
The class body
4.2.2
The point is as follows ：
1. Class name must match “ identifier ” The rules of ; General rules , title case , Use more than one word “ Hump principle ”.
2. In the class body, we can define properties and methods .
3. Attributes are used to describe data , Method ( It's a function ) Used to describe operations related to these data .
4.2.3 _init__ Construction method and __new__ Method
Classes are abstract , Also known as “ Templates for objects ”. We need to use this template through the class , Create instance object of class , Then you can use the functions defined by the class .
individual Python The object contains the following parts ：
1.id（identity Identification code ）
2.type（ object type ）
3.value（ The value of the object ）
(1) attribute （attribute）
(2) Method （method）
4.3 Instance properties and instance methods
4.3.1 Instance attributes
Instance properties are properties that are subordinate to instance objects , Also known as “ Instance variables ”
4.3.2 Example method
Instance methods are methods that are subordinate to instance objects . The definition format of the instance method is as follows ：
def Method name (self[, Parameter list ])：
Function body method
The call format is as follows ：
object . Method name ([ Argument list ])
4.3.3 The difference between function and method
1. They are all statement blocks used to complete a function , The essence is the same .
2. Method call , Call through object . Method is subordinate to a specific instance object , Ordinary functions do not have this feature .
3. Intuitively , Method definition needs to pass self, The function doesn't need .
4.3.4 Class object 、 Class properties 、 Class method 、 Static methods
5 Memory analysis instance object and class object creation process
6._del__ Method ( Destructor ) And garbage collection mechanisms
_del__ The method is called “ destructor ”, Used to implement the operations required when the object is destroyed .
