python之callable

Posted 2021-01-03 stay hungry stay foolish

callback是python的内置函数

英文说明:

callable(object)

　　Return True If the object argument appears callable，False if Not. If this return true，it is still posssible 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 instence) ; instance  are callable if theri 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()括号的方式调用

 

2 可调用对象，在实际调用也可能失败；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，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.

　　

转载：https://www.cnblogs.com/sesshoumaru/p/5983979.html