Python 判断变量的类型

这里有两种方法。type 和isinstance

import types

aaa = 0
print type(aaa)
if type(aaa) is types.IntType:
    print "the type of aaa is int"
if isinstance(aaa,int):
    print "the type of aaa is int"

bbb = 'hello'
print type(bbb)
if type(bbb) is types.StringType:
    print "the type of bbb is string"
if isinstance(bbb,str):
    print "the type of bbb is string"

#if the type is NoneType,the isinstance does not work
#we should judge the NoneType like below
#if row is None
#if type(row) is types.NoneType

#In my opinion,use the types to judge the type of a param is convinient<span style="font-family:Arial;background-color: rgb(255, 255, 255);">, use the isinstance to judge whether a instance is a type of a class or not</span>

一、isinstance()

在Python中可以使用type()与isinstance()这两个函数判断对象类型，而isinstance()函数的使用上比type更加方便。

复制代码代码如下:

 # coding=utf-8

 a = 10

 def b():
     pass

 print isinstance(a,(int,str))
 print isinstance(a,(float,str))
 print isinstance(b,(str,int))

 class c:
     pass

 obj = c()

 print isinstance(obj,(c,int))

执行结果：

复制代码代码如下:

 True
 False
 False
 True

二、isinstance 和 type的区别

isinstance 和 type的区别在于：

复制代码代码如下:

 class A:
     pass

 class B(A):
     pass

 isinstance(A(), A)  # returns True
 type(A()) == A      # returns True
 isinstance(B(), A)    # returns True
 type(B()) == A        # returns False

区别就是 对于subclass之类的 type就不行了，所以,强烈建议不要使用type判断对象类型。