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
本文出自 “大云技术” 博客，请务必保留此出处http://hdlptz.blog.51cto.com/12553181/1898430
原文：http://hdlptz.blog.51cto.com/12553181/1898430