英文文档:
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.
说明:
1. 方法用来检测对象是否可被调用,可被调用指的是对象能否使用()括号的方法调用。
>>> 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. 可调用对象,在实际调用也可能调用失败;但是不可调用对象,调用肯定不成功。
3. 类对象都是可被调用对象,类的实例对象是否可调用对象,取决于类是否定义了__call__方法。
>>> class A: #定义类A pass >>> callable(A) #类A是可调用对象 True >>> a = A() #调用类A >>> callable(a) #实例a不可调用 False >>> a() #调用实例a失败 Traceback (most recent call last): File "<pyshell#31>", line 1, in <module> a() TypeError: 'A' object is not callable >>> class B: #定义类B def __call__(self): print('instances are callable now.') >>> callable(B) #类B是可调用对象 True >>> b = B() #调用类B >>> callable(b) #实例b是可调用对象 True >>> b() #调用实例b成功 instances are callable now.