一、字符串内置方法的基本使用
1 用途:记录描述性的状态,比如人的名字、地址、性别
2 定义方式:在"",'',""""""内包含一系列的字符
msg='hello' #msg=str('hello')
res1=str(1)
res2=str([1,2,3])
print(type(res1),type(res2))
info="'xxx'"
3 常用操作+内置的方法
优先掌握的操作:
1、按索引取值(正向取+反向取) :只能取
msg='hello world'
print(msg[4])
print(msg[-1])
msg[3]='A'
name='egon'
2、切片(顾头不顾尾,步长)
msg='hello world' # 就是从一个大的字符串中切分出一个全新的子字符串
print(msg[0:5])
print(msg) # 没有改变原值
print(msg[0:5:1])
print(msg[0:5])
print(msg[0:5:2]) #hlo
了解:
print(msg[0:5:1])
msg='hello world'
print(msg[5:0:-1])
print(msg[5::-1])
print(msg[-1::-1])
print(msg[::-1])
3、长度len
msg='hello world'
print(len(msg))
4、成员运算in和not in: 判断一个子字符串是否存在于一个大的字符串中
print('alex' in 'alex is dsb')
print('dsb' in 'alex is dsb')
print('sb' in 'alex is dsb')
print('xxx' not in 'alex is dsb') # 推荐
print(not 'xxx' in 'alex is dsb')
5、去掉字符串左右两边的字符strip,不管中间的
user=' egon '
user=' x egon '
user="*******egon********"
user=" **+* */***egon* **-*****"
print(user.strip("* +/-"))
user=input('>>>: ').strip()
if user == "egon":
print('用户名正确')
6、切分split:针对按照某种分隔符组织的字符串,可以用split将其切分成列表,进而进行取值
msg="root:123456:0:0::/root:/bin/bash"
res=msg.split(':')
print(res[1])
cmd='dowload|a.txt|3333333'
cmd_name,filename,filesize=cmd.split('|')
7、循环
msg='hello'
for item in msg:
print(item)
二、字符串的内置方法
需要你掌握的
1、strip,lstrip,rstrip
print('*****egon*****'.lstrip('*'))
print('*****egon*****'.rstrip('*'))
print('*****egon*****'.strip('*'))
2、lower,upper
msg='aABBBBb'
res=msg.lower()
print(res)
print(msg)
3、startswith,endswith
msg='alex is dsb'
print(msg.startswith('alex'))
print(msg.endswith('sb'))
print(msg.endswith('b'))
4、format的三种玩法
print('my name is %s my age is %s' %('egon',18))
print('my name is {name} my age is {age}'.format(age=18,name='egon'))
了解
print('my name is {} my age is {}'.format(18,'egon'))
print('my name is {0} my age is {1}{1}'.format(18,'egon'))
5、split,rsplit
msg='get|a.txt|333331231'
# print(msg.split('|',1))
print(msg.split('|',1))
print(msg.rsplit('|',1))
6、join
msg='get|a.txt|333331231'
l=msg.split('|')
print(l)
src_msg='|'.join(l)
print(src_msg)
7、replace
msg='alex say i have one tesla,alex is alex hahaha'
print(msg.replace('alex','sb',1))
print(msg)
8、isdigit # 判断字符串中包含的是否为纯数字
print('10.1'.isdigit())
age=input('>>: ').strip()
if age.isdigit():
age=int(age) #int('asfdsadfsd')
if age > 30:
print('too big')
elif age < 30:
print('too small')
else:
print('you got it')
else:
print('必须输入数字')
需要了解的内置方法
1、find,rfind,index,rindex,count
msg='hello alex is sb'
print(msg.find('alex'))
print(msg.find('alex',0,3))
print(msg.index('alex'))
print(msg.index('alex',0,3))
msg='alex aaa alex'
print(msg.find('alex'))
print(msg.rfind('alex'))
msg='alex aaa alex'
print(msg.count('alex')) # 统计一个子字符串在大字符串中出现的次数
2、center,ljust,rjust,zfill
print('egon'.center(50,'*'))
print('egon'.ljust(50,'*'))
print('egon'.rjust(50,'*'))
print('egon'.zfill(50))
3、expandtabs
print('a b'.expandtabs(1))
4、captalize,swapcase,title
print('hello'.capitalize())
print('hElLo'.swapcase())
print('egon is nb'.title())
5、is数字系列
在python3中
num1=b'4' #bytes
num2=u'4' #unicode,python3中无需加u就是unicode
num3='壹' #中文数字
num4='Ⅳ' #罗马数字
''.isnumeric(): unicode,中文数字,罗马数字
print(num2.isnumeric())
print(num3.isnumeric())
print(num4.isnumeric())
''.isdecimal(): unicode
print(num2.isdecimal())
print(num3.isdecimal())
print(num4.isdecimal())
''.isdigit() :bytes,unicode
print(num1.isdigit())
print(num2.isdigit())
print(num3.isdigit())
print(num4.isdigit())
6、is其他
print('abc你'.isalpha()) # 字符串中包含的是字母或者中文字符
字符串中包含的是字母(中文字符)或数字
print('ab'.isalnum())
print('123123'.isalnum())
print('ab123'.isalnum())
三、列表该类型总结1 存一个值