本节内容
- 列表、元组操作
- 字符串操作
- 字典操作
- 集合操作
- 文件操作
- 字符编码与转码
1. 列表、元组操作
列表是我们以后最常用的数据类型之一，通过列表可以对数据实现最方便的存储、修改等操作
定义列表
name = ["Martin","Annie","JMA","Martin","Ly"]
通过下标访问列表中的元素，下标从0开始计数
1 >>> name[0] 2 ‘Martin‘ 3 >>> name[4] 4 ‘Ly‘ 5 >>> name[-1] #可以倒着取 6 ‘Ly‘
切片:取多个元素
>>> name = ["Martin","Annie","JMA","Martin","Ly"] >>> name[1:4] #取下标1至下标4之间的数字，包括1，不包括4 [‘Annie‘, ‘JMA‘, ‘Martin‘] >>> name[0:3] #取下标0至下标3间的数字，包括0，不包括3 [‘Martin‘, ‘Annie‘, ‘JMA‘] >>> name[:3] #如果是从头开始取，0可以忽略，跟上句效果一样 [‘Martin‘, ‘Annie‘, ‘JMA‘] >>> name[3:-1] #取下标3至-1的值，不包括-1 [‘Martin‘] >>> name[3:] #如果想取最后一个，必须不能写-1，只能这么写 [‘Martin‘, ‘Ly‘] >>> name[0::2] #后面的2是代表，每隔一个元素，就取一个 [‘Martin‘, ‘JMA‘, ‘Ly‘] >>> name[::2] #和上面的效果一样 [‘Martin‘, ‘JMA‘, ‘Ly‘]
追加
>>> name.append("HZY")
>>> name
[‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘]
插入
>>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘] >>> name.insert(1,"HZY") >>> name [‘Martin‘, ‘HZY‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘]
修改
[‘Martin‘, ‘HZY‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘] >>> name[1] = "acer" >>> name [‘Martin‘, ‘acer‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘]
删除
>>> name
[‘Martin‘, ‘acer‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘]
>>> del name[1]
>>> name
[‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘, ‘HZY‘]
>>> name.remove("HZY") #删除指定元素
>>> name
[‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Ly‘]
>>> name.pop() #删除列表最后一个值
‘Ly‘
>>> name
[‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘]
扩展
>>> name2 = [1,2,3,4] >>> name.extend(name2) >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, ‘Martin‘, 1, 2, 3, 4]
拷贝
浅copy,列表的copy >>> name = ["Martin", "Annie", "JMA", ["ABC", "test"], "Martin"] >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘ABC‘, ‘test‘], ‘Martin‘] >>> name2 = name.copy() >>> name2 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘ABC‘, ‘test‘], ‘Martin‘] >>> name[3][0] ‘ABC‘ >>> name[3][0] = "abc" >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘] >>> name2 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘] 浅copy,copy模块的copy >>> import copy >>> name3 = copy.copy(name) >>> name3 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘] >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘] >>> name[3][0] = "123" >>> name3 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘123‘, ‘test‘], ‘Martin‘] >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘123‘, ‘test‘], ‘Martin‘] deepcopy，copy模块的deepcopy,一般别用 >>> import copy >>> name4 = copy.deepcopy(name) >>> name4 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘123‘, ‘test‘], ‘Martin‘] >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘123‘, ‘test‘], ‘Martin‘] >>> name[3][0] = "abc" >>> name4 [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘123‘, ‘test‘], ‘Martin‘] >>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘]
统计
>>> name
[‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘]
>>> name.count("Martin")
2
排序&翻转
>>> name [‘Martin‘, ‘Annie‘, ‘JMA‘, [‘abc‘, ‘test‘], ‘Martin‘] >>> name.sort() #排序 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: ‘<‘ not supported between instances of ‘list‘ and ‘str‘ #3.0里不同数据类型不能放在一起排序了 >>> name[3] = "test" >>> name [‘Annie‘, ‘JMA‘, ‘Martin‘, ‘test‘, ‘Martin‘] >>> name.sort() >>> name [‘Annie‘, ‘JMA‘, ‘Martin‘, ‘Martin‘, ‘test‘] >>> name.reverse() #反转 >>> name [‘test‘, ‘Martin‘, ‘Martin‘, ‘JMA‘, ‘Annie‘]
获取下标
>>> name
[‘test‘, ‘Martin‘, ‘Martin‘, ‘JMA‘, ‘Annie‘]
>>> name.index("JMA")
3
清空列表
name.clear() #清空列表
列表循环
for i in name:
for j in i:
print(j)
print(i)
元组
元组其实跟列表差不多，也是存一组数，只不是它一旦创建，便不能再修改，所以又叫只读列表
语法：
>>> name = ("Martin", "JMA", "Ly")
>>> name
(‘Martin‘, ‘JMA‘, ‘Ly‘)
它只有2个方法，一个是count,一个是index
2. 字符串操作
特性：不可修改
3. 字典操作
字典一种key - value 的数据类型，使用就像我们上学用的字典，通过笔划、字母来查对应页的详细内容。
语法：
info = {
"stud001": "xiaoming",
"stud002": "xiaohong",
"stud003": "xiaodong",
"stud004": "xiaomei"
}
字典的特性：
- dict是无序的
- key必须是唯一的
增加
info["stud005"] = "xiao"
print(info.setdefault("stud004","martin")) #key存在时打印对应value
print(info.setdefault("stud005","martin")) #key不存在时增加
修改
info["stud001"] = "xiao"
info["stud001"] += ",xiao"
{‘stud001‘: ‘xiaoming,xiao‘, ‘stud002‘: ‘xiaohong‘, ‘stud003‘: ‘xiaodong‘, ‘stud004‘: ‘xiaomei‘}
删除
info.pop("stud001") #指定删除
info.popitem() #随机删除
del info["stud002"] #python的删除方法
查找
"stud003" in info #标准用法，判断key是否在字典里，存在未Ture，不存在为False
True
print(info.get("stud001")) #这个不会，不存在会返回none
print(info["stud001"]) #该方法当key不存在时会报错
其他操作
print(info.keys()) #获取字典的key列表 print(info.values()) #获取字典的value列表 print(info.items()) #将字典转换成列表 dict_items([(‘stud001‘, ‘xiaoming‘), (‘stud002‘, ‘xiaohong‘), (‘stud003‘, ‘xiaodong‘), (‘stud004‘, ‘xiaomei‘)])
字典循环
方法1：
for key in info:
print(key,info[key])
方法二：
for k,v in info.items(): #会先把dict转成list,数据量大时莫用
print(k,v)
字典更新合并
>>> info
{‘stud001‘: ‘xiaoming‘, ‘stud002‘: ‘xiaohong‘, ‘stud003‘: ‘xiaodong‘, ‘stud004‘: ‘xiaomei‘}
>>> b
{1: 2, 3: 4}
>>> info.update(b)
>>> info
{‘stud001‘: ‘xiaoming‘, ‘stud002‘: ‘xiaohong‘, ‘stud003‘: ‘xiaodong‘, ‘stud004‘: ‘xiaomei‘, 1: 2, 3: 4}
多级字典嵌套及操作
menu = {
"jiangxi": {
"nanchang": {
"xinjianxian": ["ncu", "bank"],
"nanchangxian": ["caijingdaxue", "jishuxueyuan"]
},
"jiujiang": {
"xiushuixian": "修水县地图",
"jiujiangxian": "九江县地图"
}
},
"guangdong": {
"shenzhen": {
"longhuaqu": "龙华区地图",
"luohuqu": "罗湖区地图"
}
}
}
menu["jiangxi"]["nanchang"]["xinjianxian"][0] += " univercity"
print(menu["jiangxi"]["nanchang"]["xinjianxian"][0])
ncu univercity
程序练习
程序: 三级菜单
要求:
- 打印省、市、县三级菜单
- 可返回上一级
- 可随时退出程序
exit_flag = False
while not exit_flag:
for i in menu:
print(i)
choice = input("1>>:")
if choice in menu:
while not exit_flag:
for i2 in menu[choice]:
print("\t", i2)
choice2 = input("2>>:")
if choice2 in menu[choice]:
while not exit_flag:
for i3 in menu[choice][choice2]:
print("\t\t", i3)
choice3 = input("3>>:")
if choice3 in menu[choice][choice2]:
for i4 in menu[choice][choice2][choice3]:
print("\t\t\t",i4)
choice4 = input("4按b返回上层>>:")
if choice4 == "b":
pass
elif choice4 == "q":
exit_flag = True
if choice3 == "b":
break
elif choice3 == "q":
exit_flag = True
if choice2 == "b":
break
elif choice2 == "q":
exit_flag = True
时间： 2024-11-04 23:30:23