10.字符串str的语法

1).字符串的索引以及切片

s = 'ABCDLSESRF'
#索引
 s1 = s[0]
 print(s1)    #A
 s2 = s[2]
 print(s2)    #C
 s3 = s[-1]
 print(s3)    #F
 s4 = s[-2]
 print(s4)    #R
 #ABCD   切片 ：顾头不顾尾
 s5 = s[0:4]
 print(s5)    #ABCD
 s6 = s[0:-1]
 print(s6)    #ABCDLSESRF
 #s7 = s[:]           s6一样的
 #s8 = s[0:]         功能
 print(s7,s8)
 s9 = s[0:0]    #无表示且不报错
s = 'ABCDLSESRF'  # s[首:尾:步长]
 s10 = s[0:5:2]
 print(s10)    #ACL
s11 = s[4:0:-1]
print(s11)    #LDCB
s12 = s[3::-1]
print(s12)    #DCBA
s13 = s[3::-2]
print(s13)    #DB
s = 'ABCDLSESRF'
s14 = s[-1::-1]
print(s14)    #FRSESLDCBA
s15 = s[::-1]
print(s15)    #FRSESLDCBA

2).字符串的操作

1.首字母大写.capitalize()

s = 'alexWUsir'
s1 = s.capitalize()
print(s1)

2.全大写.upper()、全小写.lower()

s = 'alexWUsir'
s1 = s.upper()
s2 = s.lower
print(s1)
print(s2)

s_str= 'acEQ1'
you_input =input('请输入验证码，不区分大小写')
if s_str.upper() == you_input.upper():
    print('输入成功')
else:
    print('请重新输入')

3.大小写翻转.swapcase()

s3 = s.swapcase()
 print(s3)

4.每个隔开(特殊字符或者数字)的单词首字母大写.tittle()

 s = 'alex*egon-wusir'
 s4 = s.title()
 print(s4)
 s = 'fade,crazy*w4rri0r_songsong node_3'
 s4 = s.title()
 print(s4)

5.居中，空白填充.center()

 s = 'alexWUsir'
 s5 = s.center(20,'~')
 print(s5)

6.去除/t替换为空格.expandtabs()

s = 'alex\tsir'
s6 = s.expandtabs()
 print(s6)

7.字符串的长度.len()

s = 'alex\tsir'
l = len(s)
print(l)

8.以什么开头.starwish,以什么结尾.endwish

s = 'alexWUsir'
s7 =s.startswith('alex')
s71 = s.startswith('e',2,5)
print(s71,s7)

9.通过元素找索引.find()    .index

find 通过元素找索引，找不到返回-1

index 通过元素找索引，找不到报错

s = 'alexWUsir'
s8 = s.find('A')
s81 = s.index('A')
print(s81s8)

10.默认删除前后空格.strip()   .lstrip从左删   .rstrip从右删

s = 'alexWUsir%'
s9 = s.strip('%')
print(s9)
s = ' *a%lexWUsi* r%'
s91 = s.strip(' %*')
print(s91)

11.找出字符中某元素的个数.count()

s = 'alexaa wusirl'
s10 = s.count('al')
print(s10)

12.字符串切割成列表 .split()

s = ';alex;wusir;taibai'
l = s.split('a')
print(l)

13.格式化输出.format()

#format的三种玩法 格式化输出
s = '我叫{}，今年{}，爱好{}，再说一下我叫{}'.format('太白',36,'girl','太白')
print(s)
name = input('请输入名字：')
s = '我叫{0}，今年{1}，爱好{2}，再说一下我叫{0}'.format(name,36,'girl')
print(s)
name = input('请输入名字：')
s = '我叫{name}，今年{age}，爱好{hobby}，再说一下我叫{name}'.format(age=18,name=name,hobby='girl')
print(s)

14.字符串中元素的替换.replace()

s = '来看待街坊邻居复合大师街坊法好的撒见客户'
s11 = s.replace('街坊','老王',1)
print(s11)