python内置函数2-callable()

Posted 2020-08-31

Help on built-in function callable in module __builtin__:

callable(...)

    callable(object) -> bool

    

    Return whether the object is callable (i.e., some kind of function).

    Note that classes are callable, as are instances with a __call__() method.

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); class instances are callable if they have a __call__() method.

中文说明：

检查对象object是否可调用。如果返回True，object仍然可能调用失败；但如果返回False，调用对象ojbect绝对不会成功。

注意：类是可调用的，而类的实例实现了__call__()方法才可调用。

版本：该函数在python2.x版本中都可用。但是在python3.0版本中被移除，而在python3.2以后版本中被重新添加。

>>> callable(0)

False

>>> callable(‘mystring‘)

False

>>> def add(a,b):

...     return a+b

... 

>>> callable(add)

True

>>> class A:

...     def method(self):

...         return 0

... 

>>> callable(A)

True

>>> a=A()

>>> callable(a)

False

>>> class B:

...     def __call__(self):

...         return 0

... 

>>> callable(B)

True

>>> b=B()

>>> callable(b)

True

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