__call__ 在Python中

Python有一组内置方法， __call__就是其中之一。 __call__方法使Python程序员可以编写实例行为类似于函数并且可以像函数一样调用的类。当实例作为函数时；如果定义了此方法，则x(arg1, arg2, ...)是x.__call__(arg1, arg2, ...)的简写。

object() is shorthand for object.__call__()

示例 1：

class Example:
    def __init__(self):
        print("Instance Created")
      
    # Defining __call__ method
    def __call__(self):
        print("Instance is called via special method")
  
# Instance created
e = Example()
  
# __call__ method will be called
e()

输出 ：

Instance Created
Instance is called via special method

示例 2：

class Product:
    def __init__(self):
        print("Instance Created")
  
    # Defining __call__ method
    def __call__(self, a, b):
        print(a * b)
  
# Instance created
ans = Product()
  
# __call__ method will be called
ans(10, 20)

输出 ：

Instance Created
200