Python – __init__ & __call__

測試環境為 CentOS 8 x86_64 (虛擬機)

下面來看一下 __init__ & __call__ 的使用時機.

• object.__init__(self[, …]) – https://docs.python.org/3/reference/datamodel.html#object.__init__
  Called after the instance has been created (by __new__())
• object.__call__(self[, args…]) – https://docs.python.org/3/reference/datamodel.html#object.__call__
  Called when the instance is “called” as a function.

參考文章 – https://vimsky.com/zh-tw/examples/usage/__call__-in-python.html

• 範例 :

  [root@localhost ~]# vi call.py
  class Product:
      def __init__(self):
          print("Instance Created") 
    
      def __call__(self, a, b):
          print(a * b) 
  
  ans = Product() 
  
  ans(10, 20)
  

  執行結果

  [root@localhost ~]# python3 call.py
  Instance Created
  200
  

  說明:
  在建立 Instance 時就會去呼叫 __init__ (初始化函式).

  ans = Product() 
  

  執行結果

  Instance Created
  

  當 Instance 作為函數時使用就會去呼叫 __call__ 涵式.

  ans(10, 20)
  

  執行結果

  200