英文文檔：
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.
說明：
- 方法用來檢測對象是否可被調(diào)用，可被調(diào)用指的是對象能否使用()括號的方法調(diào)用塔插。
>>> 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
- 可調(diào)用對象梗摇，在實際調(diào)用也可能調(diào)用失敗想许；但是不可調(diào)用對象伶授，調(diào)用肯定不成功。
- 類對象都是可被調(diào)用對象流纹，類的實例對象是否可調(diào)用對象糜烹，取決于類是否定義了 __call__ 方法。
>>> class A: #定義類A
pass
>>> callable(A) #類A是可調(diào)用對象
True
>>> a = A() #調(diào)用類A
>>> callable(a) #實例a不可調(diào)用
False
>>> a() #調(diào)用實例a失敗
Traceback (most recent call last):
File "<pyshell#31>", line 1, in <module>
a()
TypeError: 'A' object is not callable
>>> class B: #定義類B
def __call__(self):
print('instances are callable now.')
>>> callable(B) #類B是可調(diào)用對象
True
>>> b = B() #調(diào)用類B
>>> callable(b) #實例b是可調(diào)用對象
True
>>> b() #調(diào)用實例b成功
instances are callable now.
