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