python全栈开发从入门到放弃之字符串的应用

  1 print(msg.strip()) #去掉左右两边的空白

  2

  3 hello

  4 hello

  5

  6 msg='********hello************'

  7 print(msg)

  8 print(msg.strip('*')) #指定的去掉左右两边的*

  9 ********hello************

 10

 11 hello

 12 (1)lstrip 指定去掉左边的*

 13 # print(msg.lstrip('*'))

 14 msg='********hello************'

 15 print(msg)

 16 print(msg.lstrip('*')) #指定去掉左边的*

 17 ********hello************

 18 hello************

 19

 20 (2)rstrip 指定去掉右边的连续的*

 21 # print(msg.rstrip('*'))

 22 msg='********hello************'

 23 print(msg)

 24 print(msg.rstrip('*')) #指定去掉右边的连续的*

 25 ********hello************

 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')

 1 info='root:x:0:0::/root:/bin/bash'

 2 print(info[0]+info[1]+info[2]+info[3])

 3 root

 info='root:x:0:0::/root:/bin/bash'

 print(info[0]+info[1]+info[2]+info[3])

 info='root:x:0:0::/root:/bin/bash'

 print(info[0]+info[1]+info[2]+info[3])

 info='root:x:0:0::/root:/bin/bash'

 print(info[0]+info[1]+info[2]+info[3])

 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

 print(user_l[0])

 # msg='hello world egon say hahah'

 # print(msg.split()) #默认以空格作为分隔符

 msg='hello world egon say hahah'

 print(msg.split()) #默认以空格为分隔符

 ['hello', 'world', 'egon', 'say', 'hahah']

 cmd='download|xhp.mov|3000'

 # cmd_l=cmd.split('|')

 # print(cmd_l[1])

 # print(cmd_l[0])

 # print(cmd.split('|',1))

 1 # print(len('hell 123'))

 2 print(len('hell 123')) #查看字符串的长度

 8   #字符串长度为8

 msg='hello world

 print(msg[1:3]) #1 2

 print(msg[1:4]) #1 2 3

 msg='hello world'

 print(msg[1:3]) #切出字符串子集但顾头不顾尾

 el

 oldboy_age=84

 while True:

 age=input('>>: ').strip()

 if len(age) == 0:continue

 if age.isdigit():

 age=int(age)

 else:

 print('must be int')

 #startswith,endswith

 # name='alex_SB'

 # 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

 # 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

 #replace

 # name='alex say :i have one tesla,my name is alex'

 # print(name.replace('alex','SB',1))

 name = 'alex say :i have one tesla,my name is alex'

 print(name.replace('alex','SB',1)) #在开头和结尾添加指定字符

 SB say :i have one tesla,my name is alex

 # %s对应所有字符 一一对应后面的元素

 print('my name is %s my age is %s my sex is %s' %('egon',18,'male'))

 #把{}当作一个占位符，.format调用对应每一个后面输入的字符

 print('my name is {} my age is {} my sex is {}'.format('egon',18,'male'))

 my name is egon my age is 18 my sex is male

 #根据{}里的索引来对应值，当{}没有值时默认为一一对应。

 print('my name is {0} my age is {1} my sex is {0}:{2}'.format('egon',18,'male'))

 my name is egon my age is 18 my sex is egon:male

 #根据{}里的输入的key来准确调用key对应的元素

 print('my name is {name} my age is {age} my sex is {sex}'.format(

 sex='male',

 age=18,

 name='egon'))

 my name is egon my age is 18 my sex is male

 #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，

 # find 查找

 name='goee say hello'

 print(name.find('e',1,3))

 #index 查找

 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

 name='goee say hello'

 print(name.index('s'))

 #count

 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

 name='aaaaaaaa aaaaa aaa'

 print(name.count('a'))

 16

 #join

 # info='root:x:0:0::/root:/bin/bash'

 # print(info.split(':'))

 # l=['root', 'x', '0', '0', '', '/root', '/bin/bash']

 # print(':'.join(l))

 #join 两个物体连接处

 指定分隔符默认，用:连接起来

 l=['root', 'x', '', '', '', '/root', '/bin/bash']

 print(':'.join(l))

 root:x:0:0::/root:/bin/bash

 #lower,upper

 # name='eGon'

 # print(name.lower())

 # print(name.upper())

 将大写字母全转为小写字母

 name = 'Egon'

 print(name.lower())

 egon

 将小写字母全转为大写

 name = 'Egon'

 print(name.upper())

 name='egon\thello'

 print(name)

 print(name.expandtabs(3))

 egon    hello

 egon hello

 以原有的变量的字符为中心两边添加指定数量的符号

 name='egon'

 print(name.center(30,'_'))

 _____________egon_____________

 ljust

 原有元素左对齐后面添加指定数量的符号

 name='egon'

 print(name.ljust(30,'*'))

 egon**************************

 rjust

 原有元素右对齐，往左边添加指定数量的符号

 name='egon'

 print(name.rjust(30,'*'))

 captalize

 首字母大写，其余部分小写

 name='eGOn'

 print(name.capitalize())

 Egon

 title

 每个单词的首字母大写

 msg='egon say hi'

 print(msg.title())

 swapcase

 小写互相对调大写变小写，小写变大写

 name='eGOn'

 print(name.swapcase())

 EgoN

  1 isdigit 是否为数字

  2 判断字符串里是否为数字，是则返回True，不是则返回False

  3

  4 num0=''

  5 num1=b'' #bytes

  6 num2=u'' #unicode,python3中无需加u就是unicode

  7 num3='四' #中文数字

  8 num4='Ⅳ' #罗马数字

  9

 10 print(num0.isdigit())

 11 print(num1.isdigit())

 12 print(num2.isdigit())

 13 print(num3.isdigit())

 14 print(num4.isdigit())

 #isdecimal:str,unicode

 # num0='4'

 # num1=b'4' #bytes

 # num2=u'4' #unicode,python3中无需加u就是unicode

 # num3='四' #中文数字

 # num4='Ⅳ' #罗马数字

 # print(num0.isdecimal())

 # # print(num1.)

 # print(num2.isdecimal())

 # print(num3.isdecimal())

 # print(num4.isdecimal())

 isdecimal

 判断一个数是否为十进制数，是则返回True,不是则返回False

 num0=''

 num1=b''

 num2=u''

 num3='四'

 num4='Ⅳ'

 print(num0.isdecimal())

 print(type(num1))

 print(num2.isdecimal())

 print(num3.isdecimal())

 print(num4.isdecimal())

 True

 <class 'bytes'>

 True

 False

 False

 #isnumeric:str,unicode,中文，罗马

 # num0='4'

 # num1=b'4' #bytes

 # num2=u'4' #unicode,python3中无需加u就是unicode

 # num3='四' #中文数字

 # num4='Ⅳ' #罗马数字

 #

 # print(num0.isnumeric())

 # # print(num1)

 # print(num2.isnumeric())

 # print(num3.isnumeric())

 # print(num4.isnumeric())

 isnumeric 同质异构的

 只针对与unicode字符的判断是否为数字，是则为真不是则为假

 num0=''

 num1=b''

 num2=u''

 num3='四'

 num4='Ⅳ'

 print(num0.isnumeric())

 print(type(num1))

 print(num2.isnumeric())

 print(num3.isnumeric())

 print(num4.isnumeric())

 True

 <class 'bytes'>

 True

 True

 True

 # name='egon123'

 # print(name.isalnum()) #字符串由字母和数字组成

 # name='asdfasdfa sdf'

 # print(name.isalpha()) #字符串只由字母组成

 #

 isalnum 字符测试

 测试变量里的元素是否为字母和数字组成

 name = 'egon123'

 print(name.isalnum())

 True