Python基於callable函式檢測物件是否可被呼叫
阿新 • • 發佈:2020-10-18
英文文件:
callable(object)
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.
檢測物件是否可被呼叫
說明:
1. 方法用來檢測物件是否可被呼叫,可被呼叫指的是物件能否使用()括號的方法呼叫。
>>> callable(callable) True >>> callable(1) False >>> 1() Traceback (most recent call last): File "<pyshell#5>",line 1,in <module> 1() TypeError: 'int' object is not callable >>>
2. 可呼叫物件,在實際呼叫也可能呼叫失敗;但是不可呼叫物件,呼叫肯定不成功。
3. 類物件都是可被呼叫物件,類的例項物件是否可呼叫物件,取決於類是否定義了__call__方法。
>>> class A: #定義類A pass >>> callable(A) #類A是可呼叫物件 True >>> a = A() #呼叫類A >>> callable(a) #例項a不可呼叫 False >>> a() #呼叫例項a失敗 Traceback (most recent call last): File "<pyshell#31>",in <module> a() TypeError: 'A' object is not callable >>> class B: #定義類B def __call__(self): print('instances are callable now.') >>> callable(B) #類B是可呼叫物件 True >>> b = B() #呼叫類B >>> callable(b) #例項b是可呼叫物件 True >>> b() #呼叫例項b成功 instances are callable now.
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