Python callable()函数用法实例分析

>>> help(callable)
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.

>>> def add(x,y):
...  return x+y
...
>>> callable(add)
True

>>> class C:
...  def printf(self):
...   print 'This is class C!'
...
>>> objC=C()
>>> callable(C)#类是可调用的，调用它们, 就产生对应的类实例.
True
>>> callable(C.printf)
True
>>> callable(objC.printf)
True

>>> class A:
...  def printf(self):
...   print 'This is class A!'
...
>>> objA=A()
>>> callable(A) #类是可调用的，调用它们, 就产生对应的类实例.
True
>>> callable(objA) #类A没有实现__call__()方法，因此，类A的实例是不可调用的
False
>>> class B:
...  def __call__(self):
...   print 'This is class B!'
...
>>> objB=B()
>>> callable(B) #类是可调用的，调用它们, 就产生对应的类实例.
True
>>> callable(objB) #类B实现了__call__()方法，因此，类B实例是可调用的
True

>>> f=lambda x,y:x+y
>>> f(2,3)
5
>>> callable(f)
True

>>> callable(2)
False
>>> callable('python')
False
>>> l=[1,2,3]
>>> callable(l)
False
>>> t=(4,5,6)
>>> callable(t)
False
>>> d={'a':1,'b':2}
>>> callable(d)
False