懒惰对象代理模块

>>> import lazy_object_proxy
>>> def expensive_func():
...     a = 2
...     b = 2
...     print("开始计算")
...     return a*b
...
>>> expensive_func()
开始计算
4
>>> obj
<Proxy at 0x0000029E6A262A48 with factory <function expensive_func at 0x0000029E6A0FD708>>
>>> print(obj)
开始计算
4
>>> obj
<Proxy at 0x0000029E6A262A48 wrapping 4 at 0x00007FFD772F7160 with factory <function expensive_func at 0x0000029E6A0FD708>>
>>> print(obj)
4

#-*-coding:GBK-*-
import lazy_object_proxy #导入懒性对象代理模块
from time import sleep
def expensive_func():
    print("Starting calculation")
    #Just as example for a very slow computation
    sleep(2)
    print("Finished calculation")
    #return the result of the calculation
    return 10
obj = lazy_object_proxy.Proxy(expensive_func)
#Function is called only when object is actually used (仅当实际使用对象时才调用函数)
print(obj) #Now expensive_func is called (expensive_func函数被调用)
print(obj) #The result without calling the expensive_func (这里的结果没有调用expensive_func函数)