Coding起來-Python設計-@Property用法

Github連結

1. 基本用法:

首先我們先來看看property很基本的用法，過去我們可能要在function裡print，它才會自動轉成我們要的文字，而return總是return一些不是我們要的而且我們也看不懂，那這邊就來看看加上@property與沒加的區別，會很清楚發現:
a. 如果不加 @property print 會得到:

<bound method house.full_information of <__main__.house object at 0x000001a8b051e988>></bound>

b. 如果加上@property print 會得到 :

##這是過去我們用print的方法: address:any Town any Street, name:Turtle, phone_number:09xx
## new method: address:any Town any Street, name:Turtle, phone_number:09xx

## property 基本用法 (有無property的區別)
class House:
    
    def __init__(self, address, name, phone_number):
        self.address = address
        self.name = name
        self.phone_number = phone_number
    
    @property
    def full_information(self):
        print("這是過去我們用print的方法:   address:%s, name:%s, phone_number:%s" %(self.address, self.name, self.phone_number))
        return "new method:  address:%s, name:%s, phone_number:%s" %(self.address, self.name, self.phone_number)
little_turtle_home = House('any Town any Street', 'Turtle', '09xx')
print(little_turtle_home.full_information)
## 如果不加 @property print 會得到 <bound method House.full_information of <__main__.House object at 0x000001A8B051E988>>
## 如果加上@property print 會得到 
## 這是過去我們用print的方法:   address:any Town any Street, name:Turtle, phone_number:09xx
##new method:  address:any Town any Street, name:Turtle, phone_number:09xx

little_turtle_home.full_information = "address:any county, name:Fish, phone_number:06xx"
## AttributeError: can't set attribute

2. 特性:

a. 用法一: property其實就是把class 底下這個function當attribute(屬性)，什麼意思呢? 它會把這個function轉成只能讀的特性，我們可以讀取 little_turtle_home.full_information，卻不能賦值給它，如果硬要賦值的話程式會報錯(AttributeError: can't set attribute)

little_turtle_home.full_information = "address:any county, name:Fish, phone_number:06xx"
## AttributeError: can't set attribute

b. 用法二: property 如何賦值? 其實就是怎麼實現 getter 、 setter 與deleter 的用法
property 如何使用 getter 、 setter and deleter，很特別只要在我們要使用的function上面加上@(function name).setter 與 @(function name).deleter 就可以囉，那getter怎麼辦?，don’t worry 它就是加上@property那個了

舉例:

介紹了@property兩種用法，它把class原本只能讀取寫死的感覺，改變成可以隨時賦予新值，這樣會讓我們在使用上彈性非常多，希望大家都有收穫!! 1. 單純的讀取方法 2. getter, setter and deleter的實現

class House:
    
    def __init__(self, name):
        self.name = name
    
    @property
    def full_name(self):
        return self.name
    
    @full_name.setter
    def full_name(self, value):
        self.name = value
    
    @full_name.deleter
    def full_name(self):
        del self.name
        print('have a nice day')
    
    
little_turtle_home = House('Turtle')
print(little_turtle_home.full_name)
## Turtle
little_turtle_home.full_name = 'Fish'
print(little_turtle_home.full_name)
## Fish
del little_turtle_home.full_name
## have a nice day
little_turtle_home.full_name = 'Star'
print(little_turtle_home.full_name)
## Star

Reference:

https://chenhh.gitbooks.io/parallel_processing/cython/python_class.html
https://www.maxlist.xyz/2019/12/25/python-property/