python数据类型和结构

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python的常量：数——整数、长整数、浮点数和复数
字符串——单引号和双引号的作用相同（与perl不同）  perl -p -i -e 's/old/new/g' filename
，三引号指示一个多行字符串，一般在定义类和函数头时做解释说明。

#!/usr/bin/python
#Filename:mymodule.py
class myModule:   
"""show  
this is only one simple example"""   
pass  
p = myModule()   
print p  


python的变量：使用变量时只需要赋值，不需要声明或定义数据类型。
python内置的三种数据结构：list、tuple和dict。

一、list常用的几种方法：append,count,extend,index,insert,pop,remove,reverse,sort
展示list用法的简单例子：

#!/usr/bin/python
#Filename:using_list.py
shoplist =['apple','mango','carrot','banana']
print 'I have',len(shoplist),'items to purchase.'
print 'These items are:'
for item in shoplist:
print item,
print '\nI also have to buy rice.'
shoplist.append('rice')
print 'My shopping list is now',shoplist
print 'I will sort my list now'
shoplist.sort()
print 'Sorted shopping list is ',shoplist
print 'The first item I will buy is ',shoplist[0]
olditem = shoplist[0]
del shoplist[0]
print 'I bought the',olditem
print 'My shopping list is now',shoplist


二、tuple与list十分相似，只是tuple和字符串一样是不可变序列。元素间用逗号分隔，为了便于识别一般会在tuple起始和结束位置加括号。
元组最通常的用法是用在打印语句中。

#!/usr/bin/python
#Filename:print_tuple.py
age = 26
name = 'SongYang'
print '%s is %d years old.' %(name,age)
print '''%s loves that girl who he is missing.
Why is %s playing with that python?''' % (name,name)