Python9-数据类型-day3

数据类型转换

#int----->str
s = 1
i = str(s)
print(i)
#str----->int
s = '123'
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