python isinstance

isinstance(object，type)常用来判断一个对象是否是一个已知的类型。 
其第参数object为对象，第二个参数type为类型名如int、str，或类型名的一个列表如[int,str,tuple,list,float]。
其返回值为布尔型（True 或 Flase）。若对象的类型与参数二的类型相同则返回True。若参数type为一个元组，参数object类型与元组中类型名之一相同也返回True。

>>> help(isinstance)
Help on built-in function isinstance in module __builtin__:

isinstance(...)
    isinstance(object, class-or-type-or-tuple) -> bool
    
    Return whether an object is an instance of a class or of a subclass thereof.
    With a type as second argument, return whether that is the object's type.
    The form using a tuple, isinstance(x, (A, B, ...)), is a shortcut for
    isinstance(x, A) or isinstance(x, B) or ... (etc.).

>>>

1、参数object为常用类型：

>>> a = 2
>>> isinstance(a,int)
True
>>> isinstance(a,float)
False
>>> type(a)
<type 'int'>
>>> s = 'abc'
>>> type(s)
<type 'str'>
>>> isinstance(s,str)
True
>>> isinstance(2.5,float)
True

2、参数object为列表、元祖、字典：

>>> lst = [1,2,'3',4]
>>> type(lst)
<type 'list'>
>>> isinstance(lst,list)
True
>>> tpl = (5,6,7)
>>> type(tpl)
<type 'tuple'>
>>> isinstance(tpl,tuple)
True
>>> dic = {a:8,b:9,c:10}

Traceback (most recent call last):
  File "<pyshell#14>", line 1, in <module>
    dic = {a:8,b:9,c:10}
NameError: name 'a' is not defined
>>> dic = {'a':8,'b':9,'c':10}
>>> isinstance(dic,dict)
True
>>> 

3、参数object为类：（建议使用isinstance判断对象，少用type。）

>>> class BaseClass:
	pass

>>> class SubClass:
	pass

>>> isinstance(BaseClass(),BaseClass)
True
>>> type(BaseClass())
<type 'instance'>
>>> type(BaseClass()) == BaseClass
False
>>> c = SubClass()
>>> isinstance(c,SubClass)
True
>>> 

4、参数type为元祖：

>>> 
>>> isinstance(c,(int,str,list))
False
>>> isinstance(c,(int,str,list,SubClass))
True
>>> t = (int,str,list,SubClass)
>>> isinstance(c,t)
True
>>>