第二（关于String & set）-优快云博客

本文介绍了Python中字符串和集合的基本操作方法，并通过具体实例展示了如何使用这些方法解决实际问题，包括字符串处理技巧及集合的数学运算。

一、string方法

字符串相加
name = 'chenkangle'
print(name.__add__('love'))

字符串包含
name = 'chenkangle'
print(name.__contains__('ka'))

字符串相等
name = 'chenkangle'
print(name.__eq__('chenkangl'))
print(name.__eq__('chenkangle'))

字符串大于等于
name = 'chenkangle'
print(name.__ge__('chenkan'))

字符串首字母大写
name = 'chenkangle'
print(name.capitalize())

字符串全部小写
name = 'ChenkAngle'
print(name.casefold())

等号为边界分隔，宽度为20个字符
name = 'ChenkAngle'
print(name.center(20,'='))

统计字符串出现的次数
name = 'today is a very good day07!'
print(name.count('da'))

字符串以什么开头
name = 'today is a very good day07!'
print(name.startswith('to'))
print(name.startswith('i',7,15))

字符串以什么结尾
name = 'today is a very good day07!'
print(name.endswith('ay'))

去掉首位的空格
name = '  today is a very good day07!    '
print(name.strip())

替换出现的子串为新串，后面的数字为替换几次，默认为-1，表示都替换
name = 'wahahaishao'
print(name.replace('ha','HA',2))

查找子串在给定的区域内首次出现的位置，从0开始
name = 'woxianghayihaishao'
print(name.index('ha',10,15))

同index作用基本一致，找字符串出现的位置，如果没有找到，返回-1，而index会报错
name = 'woxianghayihaishao'
print(name.find('hm'))

切割字符串，以给定的参数为切割符来切割，返回一个列表
name = 'woxianghayihaishao'
print(name.split('ha'))

将tab转为空格，默认是8个，可以指定
name = 'wo\thao'
print(name.expandtabs())
print(name.expandtabs(2))

format功能类似于%s
name = "today {0} is {1} fine {2}"
result = name.format('really','a','day07')
print(result)

变量的处理
name = "your {name} and your {id}"
result = name.format(name='ckl',id='893')
print(result)

序列拼接，按照指定的分隔符进行拼接
ckllist = ['c','h','u','n','t','i','a','n']
result = "-".join(ckllist)
print(result)


判断字符串内容是否为数字

num = '123'
print(num.isdigit())
#结果为true，即内容为数字

1 passwd = input('please input your pass: ').strip()
2 if len(passwd) > 0:
3     if passwd.isdigit():
4         passwd=input(passwd)
5         print(passwd)
6     else:
7         print("passwd must be a number type.")
8 else:
9     print("passwd is not empty")

二、集合

 1 s1 = {22,87,39,5,10,15}
 2 s2 = {17,15,39,22,10}
 3 
 4 #交集
 5 print(s1 & s2)
 6 print(s1.intersection(s2))
 7 
 8 #并集
 9 print(s1 | s2)
10 print(s1.union(s2))
11 
12 #差集
13 print(s1 - s2)
14 print(s1.difference(s2))
15 print(s2 - s1)
16 print(s2.difference(s1))
17 
18 #对称差集
19 print(s1 ^ s2)
20 print(s1.symmetric_difference(s2))
21 
22 #集合添加值，集合内的值必须是不可变类型，也就是列表，字典均不可
23 s1.add(3)
24 s1.add(9)
25 print(s1)
26 
27 #集合无序的，弹出内容也是无序的
28 p1 = s1.pop()
29 p2 = s1.pop()
30 print(p1)
31 print(p2)
32 print(s1)
33 
34 #集合制定删除
35 s1.remove(9) #如果值不存在会报错
36 #s1.remove(112)
37 print(s1)
38 
39 #这样的方法，不存在就不会报错
40 s1.discard(112)
41 s1.discard(10)
42 print(s1)

结果：

{10, 15, 22, 39}
{10, 15, 22, 39}
{5, 39, 10, 15, 17, 22, 87}
{5, 39, 10, 15, 17, 22, 87}
{5, 87}
{5, 87}
{17}
{17}
{17, 5, 87}
{17, 5, 87}
{3, 5, 39, 9, 10, 15, 22, 87}
3
5
{39, 9, 10, 15, 22, 87}
{39, 10, 15, 22, 87}
{39, 15, 22, 87}

三、练习超市购物程序

 1 #!/usr/bin/env python
 2 #-*- coding:utf-8 -*-
 3 import sys
 4 ShopCart = []
 5 Wallet = [30000,0]
 6 
 7 #定义商品字典包含编号、名称、价格
 8 GoodsBuyDict = {
 9     '1':{
10          'ipad':3000
11     },
12     '2':{
13          'mac':21000
14     },
15     '3':{
16         'car':29000
17     },
18     '4':{
19         'bag':1800
20      },
21     '5':{
22         'tv':2800
23      }
24 }
25 
26 #定义一个打印商品名称的方法
27 def PrintGoods():
28     print("goods list".center(32, '='))
29     for Gnum, Gdic in GoodsBuyDict.items():
30         for Goods, Price in Gdic.items():
31             print('%s No is %-5s price is :\t%s' % (Gnum, Goods, Price))
32 
33 #定义一个打印购物车清单的方法
34 def PrintGcart():
35     print("goods cart have".center(32, '*'))
36     for Gdname in ShopCart:
37         print(Gdname)
38 
39 Gbool = True
40 while Gbool:
41     PrintGoods()
42     #循环输入需要购买的商品编号
43     InputNum = input("Please input you wanna buy goods Number: ")
44 
45     #定义还能购买的商品列表，初始为空
46     CanBuyDict = {}
47 
48     #定义一个方法来收集已经购买的商品并增加到CanBuyDict字典里
49     def CanBuyFunc():
50         for GoodsPrice in GoodsBuyDict.values():
51             for Gname, Gprice in GoodsPrice.items():
52                 if Wallet[0] > Gprice:
53                     CanBuyDict[Gname] = Gprice
54 
55     #如果输入的序列号存在就开始操作
56     if InputNum in GoodsBuyDict.keys():
57         for Gk,Gp in GoodsBuyDict[InputNum].items():
58             if int(Wallet[0]) > Gp:
59                 #购物车增加商品
60                 ShopCart.append(Gk)
61                 #钱包余额剩余和化肥
62                 Wallet[0] -= Gp
63                 Wallet[1] += Gp
64             else:
65                 #执行还能购买商品的函数，并收集能购买的字典内容
66                 CanBuyFunc()
67                 print("You can not pay for this good,and your credit is running low!")
68                 print("")
69                 print("You can buy list")
70                 print("="*40)
71                 #打印还能购买商品列表
72                 for Cd,Cp in CanBuyDict.items():
73                     print("%s price is %s" %(Cd,Cp))
74         print("Your pay money is %d and left %d" % (Wallet[1], Wallet[0]))
75         #执行还能购买商品的函数，并收集能购买的字典内容
76         CanBuyFunc()
77         #如果列表为空，说明不能购买任何商品了，就退出程序
78         if CanBuyDict.__len__() < 1:
79             print("Sorry, you can't buy anything !")
80             print("")
81             PrintGcart()
82             sys.exit(1)
83     else:
84         #输入的序号不在，则继续循环
85         print("Sorry,You must choose a number in the list !")
86         continue
87     #关于是否继续购买的循环
88     while True:
89         print("")
90         ContinueBuy = input("Do you want continue to by y or n: ")
91         if ContinueBuy == 'y':
92             break
93         elif ContinueBuy == 'n':
94             #如果退出就打印购物车清单并设定循环值为False
95             PrintGcart()
96             Gbool = False
97             break
98         else:
99             print("You Must choos y or n !")