python基础2

Posted 2020-12-02 菜鸟小于

1.列表元组

列表是我们最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:

1 # yu
2 
3 names=["啦啦","嘿嘿",‘鱼鱼‘]

我们通过列表下标进行数据的提取:

1 # yu
2 names=["啦啦","嘿嘿",‘鱼鱼‘]
3 print(names)
4 print(names[0])#第一个数据从0开始
5 print(names[-1])#倒过来取值

切片:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
3 print(names[1:3])#取下标1 ,不包含下标3 [‘heihei‘, ‘yuyu‘]
4 print(names[1:-1])#取下标1至-1的值，不包括-1
5 print(names[:3])#如果是从头开始取，0可以忽略
6 print(names[3:])#取到最后一个值
7 print(names[3:-1])#取不到最后一个值
8 print(names[0::2])#后面的2是代表，每隔一个元素，就取一个

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追加:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
3 names.append("嘻嘻")
4 print(names)
5 #结果[‘lala‘, ‘heihei‘, ‘yuyu‘, ‘hehe‘, ‘haha‘, ‘嘻嘻‘]

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插入:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
3 names.insert(2,‘从2插入‘)
4 print(names)
5 #结果[‘lala‘, ‘heihei‘, ‘从2插入‘, ‘yuyu‘, ‘hehe‘, ‘haha‘]

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修改:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
3 names[1]=‘修改下标为1‘
4 print(names)
5 #结果[‘lala‘, ‘修改下标为1‘, ‘从2插入‘, ‘yuyu‘, ‘hehe‘, ‘haha‘]

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删除:

1 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
2 #names.clear()#清空列表
3 print(names)#返回[]
4 #del names[1]#删除指定下标的值
5 print(names)#[‘lala‘, ‘yuyu‘, ‘hehe‘, ‘haha‘
6 #names.remove("yuyu")#删除指定的值
7 print(names)
8 names.pop()#默认删最后一个,也可以加入你祥删除的下标
9 print(names)

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扩展:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘]
3 b=[1,2,3]
4 names.extend(b)
5 print(names)#[‘lala‘, ‘heihei‘, ‘yuyu‘, ‘hehe‘, ‘haha‘, 1, 2, 3]

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拷贝(浅拷贝与深拷贝的区别):

1 names=["Young","Jon",["Tom","Jerry"],‘Jems‘,‘Sunny‘]
2 names2 = names.copy()
3 names[1]="浅copy"
4 names[2][0]="深copy"
5 print(‘name1:‘,names)
6 print(‘name2:‘,names2)
7 #结果
8 #name1: [‘Young‘, ‘浅copy‘, [‘深copy‘, ‘Jerry‘], ‘Jems‘, ‘Sunny‘]
9 #name2: [‘Young‘, ‘Jon‘, [‘深copy‘, ‘Jerry‘], ‘Jems‘, ‘Sunny‘]

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统计:

1 # yu
2 names=["lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘,‘haha‘]
3 print(names.count(‘haha‘))#结果2

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排序:

1 # yu
2 names=["1lala","3heihei",‘5yuyu‘,‘4hehe‘,‘2haha‘,‘1haha‘]
3 names.sort()
4 print(names)

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反转:

1 names=["1lala","2heihei",‘3yuyu‘,‘4hehe‘,‘5haha‘,‘6haha‘]
2 names.reverse()
3 print(names)
4 #结果[‘6haha‘, ‘5haha‘, ‘4hehe‘, ‘3yuyu‘, ‘2heihei‘, ‘1lala‘]

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获取下标:

1 # yu
2 names=["0lala","1heihei",‘2yuyu‘,‘3hehe‘,‘4haha‘,‘5haha‘]
3 print(names.index("2yuyu"))#2

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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

定义:

names=("lala","heihei",‘yuyu‘,‘hehe‘,‘haha‘,‘haha‘)

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.

# yu
name=‘young‘
 #首字母大写
print(name.capitalize() )
# name.casefold()   大写全部变小写
print(name.center(50,"-") ) #输出----------------------young-----------------------
# name.count(‘lex‘) 统计 lex出现次数
# name.encode()  将字符串编码成bytes格式
# name.endswith("g")  判断字符串是否以g结尾
#  "Young	Y".expandtabs(10) 输出‘Young      Y‘， 将	转换成多长的空格
print(name.find(‘o‘))  #查找A,找到返回其索引， 找不到返回-1

 1 #format
 2 cata = "my name is {}, and age is {}"
 3 print(cata.format("young",23))#结果my name is young, and age is 23
 4 cata = "my name is {}, and age is {}"
 5 print(cata.format("23",‘young‘))#my name is 23, and age is young
 6 cata = "my name is {name}, and age is {age}"
 7 print(cata.format(age=23,name=‘young‘))
 8 
 9 #format_map
10 cata = "my name is {name}, and age is {age}"
11 print(cata.format_map({‘name‘:‘young‘,‘age‘:23}))

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cata = "my name is {name}, and age is {age}"
print(cata.index(‘a‘))
print(‘9aA‘.isalnum() )
print(‘9‘.isdigit() )#是否整数)
name=‘Hello‘
print(name.isnumeric  )
# name.isprintable
# name.isspace
# name.istitle
# name.isupper
print("|".join([‘lala‘,‘hihi‘,‘wow‘]))

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#maketrans
intab = "aeiou"  #This is the string having actual characters.
outtab = "12345" #This is the string having corresponding mapping character
trantab = str.maketrans(intab, outtab)
print(trantab)
str = "this is string example....wow!!!"
print(str.translate(trantab))
#     ‘th3s 3s str3ng 2x1mpl2....w4w!!!‘

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1 print(cata.partition(‘is‘))#(‘my name ‘, ‘is‘, ‘ {name}, and age is {age}‘)
2 print(cata.swapcase())#大小写互换
3 print(cata.zfill(40))
4 n=‘hello world‘
5 print(n.ljust(40, "-"))
6 print(n.rjust(40, "-"))
7 b="ddefdsdff_哈哈" 
8 b.isidentifier() #检测一段字符串可否被当作标志符，即是否符合变量命名规则

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