python全栈开发从入门到放弃之字符串的应用

Posted 2020-09-29

1、strip

strip 脱去（...的）衣服

去掉左右两边的空白msg=‘ hellprint(msg)

 

 1  1 print(msg.strip()) #去掉左右两边的空白
 2  2 
 3  3 hello
 4  4 hello
 5  5 
 6  6 msg=‘********hello************‘
 7  7 print(msg)
 8  8 print(msg.strip(‘*‘)) #指定的去掉左右两边的*
 9  9 ********hello************
10 10 
11 11 hello
12 12 (1)lstrip 指定去掉左边的*
13 13 # print(msg.lstrip(‘*‘))
14 14 msg=‘********hello************‘
15 15 print(msg)
16 16 print(msg.lstrip(‘*‘)) #指定去掉左边的*
17 17 ********hello************
18 18 hello************
19 19 
20 20 (2)rstrip 指定去掉右边的连续的*
21 21 # print(msg.rstrip(‘*‘))
22 22 msg=‘********hello************‘
23 23 print(msg)
24 24 print(msg.rstrip(‘*‘)) #指定去掉右边的连续的*
25 25 ********hello************
26 26 ********hello

#strip的用处
# while True:
# name=input(‘user: ‘).strip()
# password=input(‘password: ‘).strip()
#
# if name == ‘egon‘ and password == ‘123‘:
# print(‘login successfull‘)

 2、split 切分

 1 1 info=‘root:x:0:0::/root:/bin/bash‘
 2 2 print(info[0]+info[1]+info[2]+info[3])
 3 3 root
 4 
 5 info=‘root:x:0:0::/root:/bin/bash‘
 6 print(info[0]+info[1]+info[2]+info[3])
 7 
 8 info=‘root:x:0:0::/root:/bin/bash‘
 9 print(info[0]+info[1]+info[2]+info[3])
10 info=‘root:x:0:0::/root:/bin/bash‘
11 print(info[0]+info[1]+info[2]+info[3])
12 
13 user_l=info.split(‘:‘) #用内置方法以‘：’能把字符串类型以列表的形式呈现出来，来取值
14 print(user_l[0])
15 
16 
17 # msg=‘hello world egon say hahah‘
18 # print(msg.split()) #默认以空格作为分隔符
19 msg=‘hello world egon say hahah‘
20 print(msg.split()) #默认以空格为分隔符
21 [‘hello‘, ‘world‘, ‘egon‘, ‘say‘, ‘hahah‘]
22 
23 
24 
25 
26 cmd=‘download|xhp.mov|3000‘
27 # cmd_l=cmd.split(‘|‘)
28 # print(cmd_l[1])
29 # print(cmd_l[0])
30 
31 # print(cmd.split(‘|‘,1))

 

用处
# while True:
# cmd=input(‘>>:　‘).strip()
# if len(cmd) == 0:continue
# cmd_l=cmd.split()
# print(‘命令是:%s 命令的参数是:%s‘ %(cmd_l[0],cmd_l[1]))

 

 

 

 

3、len 长度

1 1 # print(len(‘hell 123‘))
2 2 print(len(‘hell 123‘)) #查看字符串的长度
3 8   #字符串长度为8

 

 

4、索引

根据索引来取出子字符串

 

1 msg=‘hello world
2 print(msg[1:3]) #1 2
3 print(msg[1:4]) #1 2 3
4 msg=‘hello world‘
5 print(msg[1:3]) #切出字符串子集但顾头不顾尾
6 el

5、混合应用

1 oldboy_age=84
2 while True:
3 age=input(‘>>: ‘).strip()
4 if len(age) == 0:continue
5 if age.isdigit():
6 age=int(age)
7 else:
8 print(‘must be int‘)

6、endswith

1 #startswith,endswith
2 # name=‘alex_SB‘
3 # print(name.endswith(‘SB‘)) #查找字符串结尾里是否有输入的参数，有着返回True,没有返回False
4 # print(name.startswith(‘alex‘)) #查找开头是否有输入的参数，有着返回True，没有返回False

7、replace

1 #replace
2 # name=‘alex say :i have one tesla,my name is alex‘
3 # print(name.replace(‘alex‘,‘SB‘,1))
4 name = ‘alex say :i have one tesla,my name is alex‘
5 print(name.replace(‘alex‘,‘SB‘,1)) #在开头和结尾添加指定字符
6 SB say :i have one tesla,my name is alex

8、占位符

 1 # %s对应所有字符 一一对应后面的元素 
 2 print(‘my name is %s my age is %s my sex is %s‘ %(‘egon‘,18,‘male‘))
 3 #把{}当作一个占位符，.format调用对应每一个后面输入的字符
 4 print(‘my name is {} my age is {} my sex is {}‘.format(‘egon‘,18,‘male‘))
 5 my name is egon my age is 18 my sex is male
 6 #根据{}里的索引来对应值，当{}没有值时默认为一一对应。
 7 print(‘my name is {0} my age is {1} my sex is {0}:{2}‘.format(‘egon‘,18,‘male‘))
 8 my name is egon my age is 18 my sex is egon:male
 9 #根据{}里的输入的key来准确调用key对应的元素
10 print(‘my name is {name} my age is {age} my sex is {sex}‘.format(
11 sex=‘male‘,
12 age=18,
13 name=‘egon‘))
14 my name is egon my age is 18 my sex is male

9、find、index、count查找

 1 #可以指定范围查找但顾头不顾尾，找到则返回该值的索引号，没有则返回-1不报错，
 2 # find 查找
 3 name=‘goee say hello‘
 4 print(name.find(‘e‘,1,3)) 
 5 #index 查找 
 6 可以指定范围查找但顾头不顾尾，找到则返回该字符串的索引号，没有则报错
 7 name=‘goee say hello‘
 8 print(name.index(‘s‘))
 9 
10 #count 
11 指定参数，查找字符串里的元素，有则返回这个查找的值里有多少数，有1个就返回1，2个就返回2 等等，没有则返回0
12 name=‘aaaaaaaa aaaaa aaa‘
13 print(name.count(‘a‘))
14 16

10、join

 1 #join
 2 # info=‘root:x:0:0::/root:/bin/bash‘
 3 # print(info.split(‘:‘))
 4 
 5 # l=[‘root‘, ‘x‘, ‘0‘, ‘0‘, ‘‘, ‘/root‘, ‘/bin/bash‘]
 6 # print(‘:‘.join(l))
 7 
 8 #join 两个物体连接处
 9 指定分隔符默认，用:连接起来
10 l=[‘root‘, ‘x‘, ‘0‘, ‘0‘, ‘‘, ‘/root‘, ‘/bin/bash‘]
11 print(‘:‘.join(l))
12 root:x:0:0::/root:/bin/bash

11、lower,upper大小写转换

 1 #lower,upper
 2 # name=‘eGon‘
 3 # print(name.lower())
 4 # print(name.upper())
 5 将大写字母全转为小写字母
 6 name = ‘Egon‘
 7 print(name.lower())
 8 egon
 9 
10 将小写字母全转为大写
11 name = ‘Egon‘
12 print(name.upper())

了解部分

1、expandtabs 指定参数多少个空格符

1 name=‘egon\thello‘
2 print(name)
3 print(name.expandtabs(3))
4 egon    hello
5 egon hello

2、center,ljust,rjust,zfill

 1 以原有的变量的字符为中心两边添加指定数量的符号
 2 name=‘egon‘
 3 print(name.center(30,‘_‘))
 4 _____________egon_____________
 5 
 6 ljust 
 7 原有元素左对齐后面添加指定数量的符号
 8 name=‘egon‘
 9 print(name.ljust(30,‘*‘))
10 egon**************************
11 rjust
12 原有元素右对齐，往左边添加指定数量的符号
13 name=‘egon‘
14 print(name.rjust(30,‘*‘))

3、captalize,swapcase,title

 1 captalize
 2 首字母大写，其余部分小写
 3 name=‘eGOn‘
 4 print(name.capitalize())
 5 Egon
 6 
 7 title
 8 每个单词的首字母大写
 9 msg=‘egon say hi‘
10 print(msg.title())
11 
12 swapcase
13 小写互相对调大写变小写，小写变大写
14 name=‘eGOn‘
15 print(name.swapcase())
16 EgoN

#在python3中

4、元素判断

 1  1 isdigit 是否为数字
 2  2 判断字符串里是否为数字，是则返回True，不是则返回False
 3  3 
 4  4 num0=‘4‘
 5  5 num1=b‘4‘ #bytes
 6  6 num2=u‘4‘ #unicode,python3中无需加u就是unicode
 7  7 num3=‘四‘ #中文数字
 8  8 num4=‘Ⅳ‘ #罗马数字
 9  9 
10 10 print(num0.isdigit())
11 11 print(num1.isdigit())
12 12 print(num2.isdigit())
13 13 print(num3.isdigit())
14 14 print(num4.isdigit())
15 #isdecimal:str,unicode
16 # num0=‘4‘
17 # num1=b‘4‘ #bytes
18 # num2=u‘4‘ #unicode,python3中无需加u就是unicode
19 # num3=‘四‘ #中文数字
20 # num4=‘Ⅳ‘ #罗马数字
21 # print(num0.isdecimal())
22 # # print(num1.)
23 # print(num2.isdecimal())
24 # print(num3.isdecimal())
25 # print(num4.isdecimal())
26 
27 isdecimal
28 判断一个数是否为十进制数，是则返回True,不是则返回False
29 num0=‘4‘
30 num1=b‘4‘
31 num2=u‘4‘
32 num3=‘四‘
33 num4=‘Ⅳ‘
34 print(num0.isdecimal())
35 print(type(num1))
36 print(num2.isdecimal())
37 print(num3.isdecimal())
38 print(num4.isdecimal())
39 True
40 <class ‘bytes‘>
41 True
42 False
43 False
44 
45 
46 #isnumeric:str,unicode,中文，罗马
47 # num0=‘4‘
48 # num1=b‘4‘ #bytes
49 # num2=u‘4‘ #unicode,python3中无需加u就是unicode
50 # num3=‘四‘ #中文数字
51 # num4=‘Ⅳ‘ #罗马数字
52 #
53 # print(num0.isnumeric())
54 # # print(num1)
55 # print(num2.isnumeric())
56 # print(num3.isnumeric())
57 # print(num4.isnumeric())
58 
59 isnumeric 同质异构的
60 只针对与unicode字符的判断是否为数字，是则为真不是则为假
61 num0=‘4‘
62 num1=b‘4‘
63 num2=u‘4‘
64 num3=‘四‘
65 num4=‘Ⅳ‘
66 print(num0.isnumeric())
67 print(type(num1))
68 print(num2.isnumeric())
69 print(num3.isnumeric())
70 print(num4.isnumeric())
71 True
72 <class ‘bytes‘>
73 True
74 True
75 True

5、is其他 isalnum、isalpha

 1 # name=‘egon123‘
 2 # print(name.isalnum()) #字符串由字母和数字组成
 3 # name=‘asdfasdfa sdf‘
 4 # print(name.isalpha()) #字符串只由字母组成
 5 #
 6 isalnum 字符测试
 7 测试变量里的元素是否为字母和数字组成
 8 name = ‘egon123‘
 9 print(name.isalnum())
10 True