Python3 namespaces and scopes, closure functions, adorners

I. Namespaces and Scopes

Namespaces are mappings of names and objects, like dictionaries, where key is the variable name and value is the variable

1. Namespaces

Name= ' Egon '  #定义变量def func ():  #定义函数    passclass Foo: #定义类    Pass

2. Classification of namespaces

(1) Built-in namespaces: As the Python interpreter starts, it includes exception types, built-in functions, and special methods, which can be called anywhere in the code

Print (sum) print (max) print (min) print (max ([builtinsfor])) Import i in Dir (builtins):   #打印所有的内置函数    Print (i )

(2) Global namespace: The execution of a file produces a global namespace, meaning that the name of a file-level definition is placed in that space

X=1 #全局命名空间def func ():     money=2000   #非全局    x=2    print (' func ') print (x) print (func) func ()

(3) Local namespace: A local namespace is generated when the function is called, and is only temporarily bound when the function is called, and the call ends the unbind

x=10000 #全局def func ():    x=1 #局部    def f1 ():        Pass

3. Scope

The visibility of namespaces is scope

• 1. Global scope: Built-in namespaces, global namespaces
• 2. Local scope: Local namespace

Name Lookup Order: Local Namespace---"Global namespace---" Built-in namespaces

View name in global scope: Gloabls ()

To view the name within a local scope: locals ()

Global scope Name: Globally valid, can be accessed anywhere, unless del is deleted, it will survive until file execution is complete

Local scope Name: Locally valid, can only be called at local scope, only valid at function call, end of call is invalidated

X=1000def func (y):    x=2    print (Locals ())    print (Globals ()) Func (1)
Output:

{' Y ': 1, ' X ': 2} {' __loader__ ': <_frozen_importlib_external. Sourcefileloader object at 0x10c436c88>, ' __package__ ': None, ' __cached__ ': None, ' __file__ ': '/users/hexin/ pycharmprojects/py3/day4/2.py ', ' func ': <function func at 0x10c3c9f28>, ' __builtins__ ': <module ' builtins ' ( built-in), ' __spec__ ': None, ' __doc__ ': None, ' time ': <module ' time ' (built-in), ' __name__ ': ' __main__ ', ' x ': 1 000}

Four. Closure function

To put it simply, a closure is what you call a function A, and the function a returns a function B to you. The returned function, B, is called a closure.

The closure function must meet the following conditions:

1. Define the internal function;
2. Contains references to external scopes rather than global scopes;

Def f1 ():    x = 1    def f2 ():        print (x)    return f2f=f1 () print (f) x=100f () print (x)

Output:

<function F1.<locals>.f2 at 0x107714400>1100

Application of closures

From urllib.request import urlopendef index (URL):    def get ():        return Urlopen (URL). Read ()    return getoldboy= Index (' http://crm.oldboyedu.com ') print (Oldboy (). Decode (' Utf-8 '))

Five. Decorative Device

1. Definition

Adorner: A tool that modifies others, modifies a function, and a tool refers to a function.

The adorner itself can be any callable object, the decorated object can also be any callable object

2. Why use adorners?

Open closure principle: Closed for modification, open for expansion
Adorners are designed to add new functionality to a decorated object without modifying its source code and calling mode.

3. The implementation of the adorner

The function of the adorner is to pass the decorated function as a parameter to the function corresponding to the adorner (the function with the same name), and return the wrapped decorated function "

Directly see, where a is a function corresponding to the adorner @a, B is the function of the adorner modifier, the role of the adorner @a is:

In short: @a is passing B to a () and returning the new B = A (b)

def a (name): #与装饰器对应的函数    return name () @a #装饰器  B = A (b) def b (): #被装饰函数    print (' hexin ')

　　

Output

Hexin

The parsing process is like this:
1.python interpreter discovers @a, it calls its corresponding function (a function)
2.a function call to specify a parameter, passed in is the @a below the modified function, that is, B ()
3.a () function execution, call B (), B () print "Hexin"

Application of adorners

Import TimedefTimmer (func):defwrapper (): Start_time=time.time () func ()#index ()Stop_time=time.time ()Print('run time is%s'% (stop_time-start_time)) returnWrapper@timmer#Index=timmer (Index)defindex (): Time.sleep (1)    Print('Welcome to Index') index () output: Welcome to Indexrun Time is1.005241870880127#--------------------------------------------------------------login_user={'User': None,'Status': False}defAuth (func):defWrapper (*args,**Kwargs):iflogin_user['User'] andlogin_user['Status']: Res=func (*args,**Kwargs)returnResElse: Name=input ('Please enter user name:') Password=input ('Please enter your password:')            ifName = ='hexin'  andPassword = ='123': login_user['User']='hexin'login_user['Status']=TruePrint('\033[45mlogin successful\033[0m') Res=func (*args,**Kwargs)returnResElse:                Print('\033[45mlogin err\033[0m')    returnWrapper@auth#Index=auth (Index)defindex ():Print('Welcome to Index page') @auth#Home=auth (Home)defHome (name):Print('%s Welcome to Home page'%name) index () Home ('hexin') Output: Please enter your user name: HEIXN Please enter your password:123Login Err Please enter your username: hexin Please enter your password:123Login Successfulhexin Welcome to Home Page

The basic frame of the adorner:

def timer (func):    def wrapper ():        func ()    return wrapper

With parameters

def timer (func):    def wrapper (*args,**kwargs):        func (*args,**kwargs)    return wrapper

Python3 namespaces and scopes, closure functions, adorners