一、闭包

1、闭包的概念

• 闭包函数必须返回一个函数对象
• 闭包函数返回的函数必须应用外部变量

2、示例

 1 def f1(a, b):
 2     def f2(x):
 3         return a*x+b
 4     return f2
 5 
 6 
 7 test1 = f1(2, 1)
 8 test2 = f1(3, 2)

 9 print(test1(10))  # 21
10 print(test2(10))  # 32


11 print(test1)  # <function f1.<locals>.f2 at 0x000002D89A3C68C8>
12 print(test2)  # <function f1.<locals>.f2 at 0x000002D8AAAF09D8>


#__closure__属性返回一个元组，包含闭包引用的外部变量
13 print(test1.__closure__)  # (<cell at 0x000002D8ABD9A768: int object at 0x00007FFC2D18B370>, <cell at 0x000002D8ABD9A708: int object at 0x00007FFC2D18B350>)
14 print(test2.__closure__)  # (<cell at 0x000002D8ABD9A7F8: int object at 0x00007FFC2D18B390>, <cell at 0x000002D8ABD9A7C8: int object at 0x00007FFC2D18B370>)
15 for i in test1.__closure__:
16     print(i.cell_contents)  # 2   # 1