python中isinstance的用法

Isinstance(

object, classinfo)

Return true if the
object argument is an instance of the
classinfo argument, or of a (direct or indirect) subclass thereof. Also return true if
classinfo is a type object and
object is an object of that type. If
object is not a class instance or an object of the given type, the function always returns false. If
classinfo is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence
types are not accepted). If classinfo is not a class, type, or tuple of classes, types, and such tuples, a
TypeError exception is raised.
Changed in version 2.2: Support for a tuple of type information was added.

isinstance說明如下:

其第一個參數為對象，第二個為類型名或類型名的一個列表。其傳回值為布爾型。若對象的類型與參數二的類型相同則返回True。若參數二為一個元組，則若物件類型與元組中類型名之一相同即返回True。

執行個體:

Python可以得到一個對象的類型 ，利用type函數：

>>>lst = [1, 2, 3]
>>>type(lst)
<type 'list'>
以利用isinstance函數，來判斷一個對象是否是一個已知的類型。

>>>isinstance(lst, list)
Trueisinstance(lst, (int, str, list))
True

>>> isinstance('iioo',(str))  
true

>>> isinstance(32434,(int))    
true

>>> isinstance('safasdf',(int,long))  
false

用cmp來比較整數的大小

>>> cmp(3,2)      
1

>>> cmp(20,30)   
-1