Python入門學習筆記9：Python高階語法與用法-列舉、函數語言程式設計<閉包>

阿新 • • 發佈：2020-07-09

  1 #Python高階語法與用法
  2 #列舉
  3 from enum import Enum, IntEnum,unique
  4 
  5 
  6 class VIP(Enum):
  7     YELLOW = 1
  8     GREEN = 2
  9     BLACK = 3
 10     RED = 4
 11 
 12 class VIP1(Enum):
 13     YELLOW = 1
 14     YELLOW_ALIAS = 1#別名
 15     GREEN = 2
 16     BLACK = 3
 17     RED = 4
 18 
 19 
 @unique#裝飾器：作用為鑑別若常量有相同時會進行報錯處理
 20 class VIP2(IntEnum):#整數型限制
 21     YELLOW = 1
 22     GREEN = 2
 23     BLACK = 3
 24     RED = 4
 25 
 26 
 27 print("name:",VIP.YELLOW.name,",value:",VIP.YELLOW.value)
 28 #變數
 29 yellow = 1
 30 green = 2
 31 #字典
 32 {'yellow':1,'green':2}
 33 #類下的類變數
 34 
 35 
 36 
 class TypeDiamond():
 37     yellow = 1
 38     green = 2
 39 
 40 """
 41 列舉的特點：
 42 常量（不可變）、防止相同值的功能
 43 列舉中的變數名稱不能重複
 44 常量相同，變數不同時
 45 列舉型別無法例項化的
 46 設計模式（23中設計模式）：單例模式
 47 """
 48 print(VIP1.YELLOW)
 49 print(type(VIP.GREEN.name))#<class 'str'>
 50 print(type(VIP.GREEN))#<enum 'VIP'> 

 51 print(VIP['GREEN'])#VIP.GREEN
 52 
 53 for vip in VIP:
 54     print(vip)
 55 for vip1 in VIP1.__members__.values():#遍歷時包含別名
 56     print(vip1)
 57     print(vip1.value)
 58 
 59 result = VIP.GREEN == VIP1.GREEN
 60 result1 = VIP.GREEN is VIP.GREEN
 61 print(result,result1)#False True
 62 
 63 
 64 a = 1
 65 print(VIP(a))#VIP.YELLOW
 66 if VIP(a) == VIP.YELLOW:
 67     print("VIP YELLOW")
 68 if VIP(a) == VIP.BLACK:
 69     print("VIP BLACK")#VIP YELLOW
 70 
 71 #函數語言程式設計
 72 
 73 #Python一切皆物件
 74 #閉包 = 函式+環境變數(函式定義的時候)
 75 
 76 
 77 def curve_pre():
 78     a1 = 25
 79 
 80     def curve(x):
 81         return a1*x*x
 82     return curve
 83 
 84 a2 = 10
 85 f = curve_pre()
 86 f(2)#等價於curve(2)
 87 print(type(f),f(2),f.__closure__,f.__closure__[0].cell_contents)#<class 'function'> 100 (<cell at 0x10488a790: int object at 0x10455cda0>,) 25
 88 
 89 a3 = 10
 90 
 91 
 92 def f3(x):
 93     return a3 * x * x
 94 
 95 
 96 print(f3(2))
 97 
 98 #閉包的事例
 99 
100 
101 def f1():
102     a4 = 10#此處為該閉包的環境變數
103 
104     def f2():
105         #a = 20   #a此處將被Python認為是一個區域性變數(無法呼叫外部環境變數導致無法形成閉包，所以此時不能將a進行賦值)
106         #print(a)
107         return a4
108     #print(a)#第一步
109     #f2()#第二步
110     #print(a)#第三步
111     return f2
112 
113 
114 f1 = f1()
115 print('f1:',f1,',f.__closure__:',f1.__closure__)
116 
117 
118 origin = 0
119 
120 
121 def go(step):
122     global origin #global關鍵字定義全域性變數且記錄並累加
123     new_pos = origin +step
124     origin = new_pos
125     return origin
126 
127 
128 print(go(2))
129 print(go(3))
130 print(go(6))
131 
132 origin1 = 0
133 
134 
135 def factory(pos):
136     def go1(step):
137         nonlocal pos#不是本地的全域性變數
138         new_pos = pos + step
139         pos = new_pos
140         return new_pos
141     return go1
142 
143 
144 tourist = factory(origin1)
145 print(tourist(2))
146 print(tourist.__closure__[0].cell_contents)
147 print(tourist(3))
148 print(tourist.__closure__[0].cell_contents)
149 print(tourist(6))
150 print(tourist.__closure__[0].cell_contents)