tuple-2

# -*- coding: utf-8 -*-
"""
Created on Tue Jun 03 21:17:59 2014

@author: Administrator
"""

# conversions and immutability
T = ( 'cc', 'aa', 'dd', 'bb' )
tmp = list( T )
tmp.sort()
print tmp

T = tuple( tmp )
print T

##################################
T = ( 1, 2, 3, 4, 5 )
L = [ x + 20 for x in T ]
print L

##################################
T = ( 1, [ 2, 3 ], 4 )

# error!
T[1] = 'spam'
T[1][0] = 'spam'

 tuple可看作对象的一种简单的关联，而list可视作一种数据结构，随着时间而改变

tuple与其他编程语言中的常量声明有点相似，可用作list不可担当的地方—作为字典的键值