本文不扯 __call__ 與 callable 這些定義, 自己去看官網.
但用一個自己可以理解的範例來示範…
官方對於 callable 的解說 (下面那個別鳥它)
Return True if the object argument appears callable, False if not. If this returns True, it is still possible that a call fails, but if it is False, calling object will never succeed. Note that classes are callable (calling a class returns a new instance); instances are callable if their class has a call() method.
Spec:
車主去買車, 車子需要插對鑰匙才能發動. 如果差錯鑰匙, 就沒辦法啟動
Example
class Car:
def __init__(self, owner: str = None):
self.owner = owner
self.ready = False
self._car_key = f"{self.owner}'s car key"
def __start(self):
print('引擎啟動')
self.ready = True
def go(self):
if self.ready:
print(f'{self.owner} 的車開始狂飆')
else:
print(f'沒反應')
def __call__(self, car_key: str):
if car_key != self._car_key:
print('插不進去')
else:
self.__start()
關於 __call__, 如果它定義在類別裡面, 表示這個類別建立出來的實例可以被調用. 所謂的 調用 這個詞, 就是某個變數後面加上 .() 的概念啦(甚至還可以接參數)!!
接續上面的範例:
toyota1 = Car('tony')
toyota1("tony's car key") # 引擎啟動
toyota1.go() # tony 的車開始狂飆
toyota2 = Car('tony')
toyota2("home_key") # 插不進去
toyota2.go() # 沒反應