python 列表、元组、字符串、字典、集合、return等梳理

有必要对这些数据类型及操作做下梳理：

1.列表：增删改查　　

a.查找：

 >>> names=["zhang","wang","li","zhao"]
 #列表天生具有下标，基于下标0,1,2,...进行查找
 >>> names[1]
 'wang'
 #列表的切片，即也是基于下标进行操作
 >>> names[1:3]
 ['wang', 'li']
 >>> names[-1:]
 ['zhao']
 >>> names[:3]
 ['zhang', 'wang', 'li']
 >>> names[1:]
 ['wang', 'li', 'zhao']
 #基于列表中的值找下标
 >>> print(names.index('li'))
 2
 >>> print(names[names.index('li')])
 li
 #基于for循环查找列表值
 >>> for i in names:
 ...     print(i)
 ...
 zhang
 wang
 li
 zhao

b.修改

 >>> names=["zhang","wang","li","zhao"]
 >>> names.append("Sun")
 >>> names
 ['zhang', 'wang', 'li', 'zhao', 'Sun']
 >>> names.insert(1,'qian')
 >>> names
 ['zhang', 'qian', 'wang', 'li', 'zhao', 'Sun']
 >>> names[2] = 'gao'
 >>> names
 ['zhang', 'qian', 'gao', 'li', 'zhao', 'Sun']

c.删除

 >>> names
 ['zhang', 'qian', 'gao', 'li', 'zhao', 'Sun']
 >>> names.remove('zhang')
 >>> names
 ['qian', 'gao', 'li', 'zhao', 'Sun']
 >>> del names[1]
 >>> names
 ['qian', 'li', 'zhao', 'Sun']
 >>> names.pop()
 'Sun'
 >>> names.pop(1)
 'li'
 >>> names
 ['qian', 'zhao']

d.增加

 >>> names
 ['qian', 'zhao']
 >>> names.append('Sun') #追加
 >>> names
 ['qian', 'zhao', 'Sun']
 >>> names.insert(1,'zhang')  #插入
 >>> names
 ['qian', 'zhang', 'zhao', 'Sun']
 >>> names2=[1,2,3,4]
 >>> names.extend(names2) #合并
 >>> names
 ['qian', 'zhang', 'zhao', 'Sun', 1, 2, 3, 4]
 #深浅copy
 >>> names3 = names.copy()#浅copy，指向同一块内存地址
 >>> names
 ['qian', 'zhang', 'zhao', 'Sun', 1, 2, 3, 4]
 >>> names3
 ['qian', 'zhang', 'zhao', 'Sun', 1, 2, 3, 4]
 #深copy，新增一块内存地址，把数据完全copy一份到新内存
 >>> import copy
 >>> names
 ['qian', 'zhang', 'zhao', 'Sun', 1, 2, 3, 4]
 >>> names4 = copy.deepcopy(names)
 >>> names4
 ['qian', 'zhang', 'zhao', 'Sun', 1, 2, 3, 4]

2.元组：只能查询和切片，也叫只读列表，只有count和index方法

 >>> names = ('alex','wang','eric')
 >>> names.append('li')
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 AttributeError: 'tuple' object has no attribute 'append'
 >>> names[1]
 'wang'

 >>> print(names.index('alex'))
 0
 >>> print(names[names.index('alex')])
 alex

3.字符串：文件中只能存储字符串，且不可修改

 name="my name is alex"
 print(name.center(50,"-")) 打印50个字符，不够用-补上，并把name放中间
 -----------------my name is alex------------------
 >>> print(name.startswith('my')) #判断是否以某字符开头
 True
 print(name.endswith("ex")) 判断name字符串是否以ex结尾
 My name is alex

 name="my\tnameis{name}andmyageis{year}old"
 print(name.format(name='alex',year=23))
 my name is alex and my age is 23 old
 print(name.index('a'))
 5
 print(''.isdigit())是否为整数
 True
 print('+'.join(['','','','']))  经常用
 1+2+3+4
 print('alexli'.replace('l','L')) 把小写l替换成大写的L
 aLex Li
 print('alex li'.split())把字符串按空格组成一个列表
 ['alex', 'li']

4.字典：key：value的数据类型，无序

>>> info = {'stu1101':'wang','stu1102':'zhang','stu1103':'li'}

a.增加

 >>> info = {'stu1101':'wang','stu1102':'zhang','stu1103':'li'}
 >>> info['stu1104'] = 'zhao'
 >>> info
 {'stu1101': 'wang', 'stu1102': 'zhang', 'stu1103': 'li', 'stu1104': 'zhao'}

 #合并
 >>> info2 = {1:3,2:5}
 >>> info.update(info2)
 >>> info
 {'stu1101': 'wang', 'stu1102': 'zhang', 'stu1103': 'li', 'stu1104': 'zhao', 1:
 , 2: 5}

b.修改

 >>> info = {'stu1101':'wang','stu1102':'zhang','stu1103':'li'}
 >>> info['stu1101'] = 'lu'
 >>> info
 {'stu1101': 'lu', 'stu1102': 'zhang', 'stu1103': 'li'}

c.删除

 >>> info
 {'stu1101': 'lu', 'stu1102': 'zhang', 'stu1103': 'li'}
 >>> del info['stu1101']
 >>> info
 {'stu1102': 'zhang', 'stu1103': 'li'}

 info.pop("stu1101")  #pop删除
 info.popitem()随机删除

d.查询

 >>> info
 {'stu1102': 'zhang', 'stu1103': 'li'}
 >>> info['stu1102']
 'zhang'
 #判断是否存在字典中
 print(info.get('stu1104'))  安全获取的方法
 None
 >>> print('stu1103' in info)
 True

 >>> info
 {'stu1102': 'zhang', 'stu1103': 'li'}
 >>> info['stu1102']
 'zhang'
 >>> for i in info:  #最建议的查询方式
 ...     print(i,info[i])
 ...
 stu1102 zhang
 stu1103 li
 >>> for k,v in info.items():
 ...     print(k,v)
 ...
 stu1102 zhang
 stu1103 li

 >>> print(info.items())
 dict_items([('stu1102', 'zhang'), ('stu1103', 'li')])

e.多级字典的查询方式

5.集合：无序，天生去重

 >>> list = [1,2,3,4]
 >>> list_1 = set(list)
 >>> print(type(list_1),list_1)
 <class 'set'> {1, 2, 3, 4}

关系型测试：

交差并子父对称集操作

a.增加

 >>> list = [1,2,3,4]
 >>> list_1 = set(list)
 >>> print(type(list_1),list_1)
 <class 'set'> {1, 2, 3, 4}
 >>> list_1.add(999)
 >>> list_1
 {1, 2, 3, 4, 999}
 >>> list_1.update([777,888])
 >>> list_1
 {1, 2, 3, 4, 999, 777, 888}

b.删除

 >>> list_1.remove(999)
 >>> list_1
 {1, 2, 3, 4, 777, 888}
 >>> list_1.discard(888)
 >>> list_1
 {1, 2, 3, 4, 777}
 >>> list_1.pop()
 1

c.深浅复制，跟列表一样

d.判断

len(list_1)  #测试长度

判断是否存在集合中，大于小于等

6.return

两个作用：

1.得到程序的执行结果；

2.程序结束，return后的代码不再执行；