Python9-数据类型-day3

数据类型转换

#int----->str
s = 1
i = str(s)
print(i)
#str----->int
s = ''
i = int(s)
print(i)
#int------->bool
i = 3
b = bool(i)
print(b)

# s = '' ------>Fasle

#非空字符串都是True

#s = "0" --------->True

字符串的索引与切片

切片：顾头不顾尾

s = 'ABCDLSESRF'
s1 = s[0]
print(s1)
s2 = s[2]
print(s2)
s3 = s[0:3]  #顾头不顾定
print(s3)
s4 = s[-1]
print(s4)
s5 = s[0:]
print(s5)
s6 = s[:]
print(s6)
s7 = s[0:5:2]
print(s7)
 
s8 = s[3::-1]
print(s8)
s9 = s[3::-2]
print(s9)
s10 = s[-1::-1]
print(s10)
s10 = s[::-1]
print(s10)

A
C
ABC
F
ABCDLSESRF
ABCDLSESRF
ACL
DCBA
DB
FRSESLDCBA
FRSESLDCBA

字符串操作

s = 'alexusir'
s1 = s.capitalize()   #首字母大写
print(s1)
 
Alexusir

s2 = s.upper()    #全部字母大写
print(s2)
############
ALEXUSIR

s3 = s.lower()    #全部字母小写
print(s3)
 
alexusir

s4 = s.swapcase()  #字母大小写翻转
print(s4)
 
aLEXUSIR

每个隔开（特殊字符或者数字）的单词的字母大写

s = 'alex open user'
s5 = s.title()
print(s5)
###########
Alex Open User

居中和填充

s = 'alexUser'
s6 = s.center(20,'#')  #居中和填充
print(s6)
 
######alexUser######

table 键位

s = 'all\tuser'
s7 = s.expandtabs()    #table键
print(s7)
 
all     user

字符长度

s = '123dfjlasjflasjfklasjf地方'
s8 = len(s)
print(s8)
 
24

判断字符串中以什么开头和结尾

s = 'alexWUsir'
s9 = s.startswith('alex')
print(s9)
 
True

s = 'alexWUsir'
s9 = s.startswith('alex')
print(s9)
s10 = s.startswith('U',5)
print(s10)
 
True
True

前缩进后缩进

s = '    string     '
s12 = s.strip()
print(s12)
 
string

username = input('请输入姓名： ').strip()
if username == "tim":
    print('gogogogo')

计数

s = 'alexaa wusiral'
s10 = s.count('al')
print(s10)
 
2

split

s = 'cis h3 c'
s11 = s.split()
print(s11)
 
s = 'cis:h3:c'
s12 = s.split(':')
print(s12)
 
['cis', 'h3', 'c']
['cis', 'h3', 'c']

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('tim',22,'girl','tim')
print(s)
s = '我叫{0},今年{1},爱好{2},再说一下我叫{0}'.format('tim',22,'girl','tim')
print(s)
 
s = '我叫{name},今年{age},爱好{hobby},再说一下我叫{name}'.format(name='tim',hobby='girl',age=33)
print(s)
 
我叫tim,今年22,爱好girl,再说一下我叫tim
我叫tim,今年22,爱好girl,再说一下我叫tim
我叫tim,今年33,爱好girl,再说一下我叫tim

字符串替换

s = 'skdfjlasdfjlasdfjlsdfjls'
s13 = s.replace('jl','xxxxxxxxxxxxxxx')
print(s13)
s14 = s.replace('jl','xxxxxxxxxxxxxxx',1)
print(s14)
 
skdfxxxxxxxxxxxxxxxasdfxxxxxxxxxxxxxxxasdfxxxxxxxxxxxxxxxsdfxxxxxxxxxxxxxxxs
skdfxxxxxxxxxxxxxxxasdfjlasdfjlsdfjls