Python记录2：数据类型

一Python的数据类型可以分为可变与不可变两种：

可变类型：值改变，但是id不变，证明就是在改变原值，就是可变类型

如list   dict 列表和字典都是可变类型

不可变类型：值改变，id也跟着改变了，证明就是不可变类型，入

Int  float  str都是不可变类型

一，字符串类型

1、用途: 性别\爱好等描述性质的状态

2、定义方式

# s1="hello" # s1=str(‘hello‘)

#str 可以将任意其他类型都转成str类型

# res=str({‘a‘:1}) #res="{‘a‘:1}"

# 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

取值正向取标号是从0开始递增，反向取标号是从-1开始递减

s1="hello world"

# print(s1[0])

# print(s1[-1])

# print(s1[-3])

# s1[0]=‘H‘

# print(s1)

#2、切片(顾头不顾尾，步长):从大字符串中切出一个子字符串

# s1="hello world"

# res=s1[1:5]

# print(s1)

# print(res)

# print(s1[0:7:1]) #0 1 2 3 4 5 6

# print(s1[0:7:2]) #0 2 4 6

# 取值之后用加号运算符也可以实现切片的功能

# print(s1[-1]+s1[-2]+s1[-3]+s1[-4]+s1[-5])

# print(s1[-1::-1]) # -1 -2

# print(s1[::-1]) # -1 -2

#3、长度len

# s1="hello world"

# print(len(s1)) # 字符的个数

#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字符串中

# msg=‘my name is alex,alex is dsb‘

# print(‘alex‘ in msg)

# print(‘egon‘ not in msg)

#5、移除空白strip: 移除字符串左右两边的字符空格

# name=input(‘username>>>: ‘).strip() #name=‘egon ‘

# name=name.strip()

# if name == ‘egon‘:

#     print(‘认证成功‘)

# msg=‘    he    llo     
‘

# res=msg.strip(‘ ‘)

# print(msg)

# print(res)

# msg=‘******hello*************‘

# res=msg.strip(‘*‘)

# print(res)

# msg=‘***&^#***hello***=-/?**‘

# print(msg.strip(‘*&^$/-?#=‘))

#6、切分split: 把一個有規律的字符串按照某個字符進行切分,切成列表

# info=‘root:x:0:0::/root:/bin/bash‘

# res=info.split(‘:‘,maxsplit=-1)

# print(res)

# cmd=‘get|a.txt|3333‘

# res=cmd.split(‘|‘)

# print(res)

# info=‘‘

# userinfo=[‘root‘, ‘x‘, ‘0‘, ‘0‘, ‘‘, ‘/root‘, ‘/bin/bash‘]

# for item in userinfo:

#     item+=‘:‘

#     info+=item

# info=info.strip(‘:‘)

# print(info,type(info))

# userinfo=[‘root‘, ‘x‘, ‘0‘, ‘0‘, ‘‘, ‘/root‘, ‘/bin/bash‘]

# res=‘:‘.join(userinfo)

# print(res,type(res))

#7、循环

# msg=‘hello‘

# for item in msg:

#     print(item)

# 需要掌握的操作(****)

#1、strip,lstrip,rstrip

# print(‘****egon****‘.strip(‘*‘))

# print(‘****egon****‘.lstrip(‘*‘))

# print(‘****egon****‘.rstrip(‘*‘))

#2、lower,upper

# x=‘ABBBBddd1231‘

# print(x.lower())

# print(‘ABBBBddd2123‘.upper())

#3、startswith,endswith

# print(‘alex is sb‘.startswith(‘alex‘))

# print(‘alex is sb‘.startswith(‘al‘))

# print(‘alex is sb‘.endswith(‘sb‘))

#4、format的三种玩法  这个参数要一一对应，中间用逗号隔开

# msg=‘my name is %s my age is %s‘ %(‘egon‘,18)

# print(msg)

# msg=‘my name is {name} my age is {age}‘.format(age=18,name=‘egon‘)

# print(msg)

# 了解

# msg=‘my name is {} my age is {}‘.format(18,‘egon‘)

# print(msg)

# msg=‘my name is {0} my age is {0}{1}{1}‘.format(18,‘egon‘)

# print(msg)

# x1=‘egon‘

# x2=(‘egon111‘)

# print(x1,x2,type(x1),type(x2))

#5、split,rsplit

# print(‘a:b:c:d:e‘.split(‘:‘,maxsplit=1))

# print(‘a:b:c:d:e‘.rsplit(‘:‘,maxsplit=1))

#6、join

#7、replace

# msg=‘alex is alex hahahah alex‘

# res=msg.replace(‘alex‘,‘SB‘,1)

# print(msg)

# print(res)

#8、isdigit

# print(‘1010101‘.isdigit())

# age=input(‘>>>: ‘)

# if age.isdigit():

#     age=int(age)

#     if age > 10:

#         print(‘too Big‘)

#     elif age < 10:

#         print(‘too small‘)

#     else:

#         print(‘you got it‘)

# else:

#     print(‘必須輸入數字‘)

# 其他操作（了解即可）

#1、find,rfind,index,rindex,count

# print("abcdefg".find(‘de‘,0,3))

# print("abcdefg".index(‘de‘))

# print("abcdefg".index(‘de‘,0,3))

# print(‘alex is alex‘.find(‘alex‘))

# print(‘alex is alex‘.rfind(‘alex‘))

# print(‘alex is alex‘.count(‘alex‘))

#2、center,ljust,rjust,zfill

# print(‘================%s===============‘ %(‘egon‘))

# print(‘egon‘.center(50,‘*‘))

# print(‘egon‘.ljust(50,‘*‘))

# print(‘egon‘.rjust(50,‘*‘))

# print(‘egon‘.zfill(50))

#3、expandtabs

# print(‘abc\tdef‘.expandtabs(8))

#4、captalize,swapcase,title

# print(‘i am egon‘.capitalize())

# print(‘aAbB‘.swapcase())

# print(‘i am egon‘.title())

#5、is数字系列

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

# ‘‘.isdigit() # bytes,unicode

# print(num1.isdigit())

# print(num2.isdigit())

# print(num3.isdigit())

# print(num4.isdigit())

# ‘‘.isdecimal():unicode

# print(num2.isdecimal())

# print(num3.isdecimal())

# print(num4.isdecimal())

# ‘‘.isnumeric():unicode,羅馬,中文

# print(num2.isnumeric())

# print(num3.isnumeric())

# print(num4.isnumeric())

#6、is其他

# name=‘egon123‘

# print(name.isalnum()) #字符串由字母或数字组成

# name=‘egon‘

# print(name.isalpha()) #字符串只由字母组成

# print(name.islower())

# print(name.isupper())

# print(name.isspace())

# print(name.istitle()

原文地址：https://www.cnblogs.com/1832921tongjieducn/p/10067862.html