Python 判斷變量的類型

這里有兩種方法。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()與isinstance()這兩個函數判斷對象類型，而isinstance()函數的使用上比type更加方便。

復制代碼代碼如下:

# 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))

執行結果：

復制代碼代碼如下:

True
False
False
True

二、isinstance 和 type的區別

isinstance 和 type的區別在於：

復制代碼代碼如下:

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

區別就是 對於subclass之類的 type就不行了，所以,強烈建議不要使用type判斷對象類型。