Python数据类型补充1

一、可变和不可变类型

可变类型: 值变了,但是id没有变,证明没有生成新的值而是在改变原值,原值是可变类型

不可变类型:值变了,id也跟着变,证明是生成了新的值而不是在改变原值,原值是不可变

# x=10
# print(id(x))
# x=11
# print(id(x))


y=['a','b','c']
print(id(y))
y[0]='A'
print(y)
print(id(y))

二、数字类型

# 其他进制=>十进制
# 十进制: 0-9
# 11 = 1*10^1 + 1*10^0

# 二进制: 0 1
# 11 = 1*2^1 + 1*2^0

# 八进制: 0-7
# 11 = 1*8^1+1*8^0

# 十六进制:0-9 A-F
# 11 = 1*16^1+1*16^0

# 十进制=>其他进制
print(bin(13)) # 十进制=>二进制 ob1101

print(oct(13)) # 十进制=>八进制 Oo15

print(hex(13)) # 十进制=>十六进制 Oxd

三、字符串

# 可以将任意类型转换成字符串
# str(1)
# str(1.3)
# x=str([1,2,3])
# print(x,type(x))

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
msg='hello world'
# print(msg[0])
# print(msg[5])
# print(msg[len(msg)-1])
# print(msg[-1])
# msg[0]='H'

2、切片(顾头不顾尾，步长): 想要从一个大字符串中切出一个小字符串
# msg='hello world'  
# print(msg[0:5])
# print(msg)
# print(msg[0:5:2]) 

3、长度len
# msg='你好啊a'
# print(len(msg))

4、成员运算in和not in
msg='yangyuanhu 老师是一个非常虎的老师'
# print('yangyuanhu' in msg)
# print('虎' not in msg)
# print(not '虎' in msg)

5、移除字符串左右两边的字符strip:默认去空格
# pwd='       1 23        '
# res=pwd.strip(' ')
# print(res)

# pwd=input('>>: ').strip() #pwd='123'
#
# if pwd == '123':
#     print('密码输入正确')

# pwd='******12*3****'
# print(pwd.strip('*'))

6、切分split:针对有规律字符串按照某个字符切成列表
# info='yyhdsb|18|female'
# li=info.split('|',1) #只按照第一个分隔符切
# print(li)

7、循环
# msg='hello'
#
# for item in msg:
#     print(item)

Conclusion：

存一个值

有序

不可变（1、可变：值变，id不变。可变==不可hash 2、不可变：值变，id就变。不可变==可hash）
s1='hello'
print(id(s1))
s1='world'
print(id(s1))


需要掌握的操作(****)
1、strip,lstrip,rstrip
print('****egon***'.strip('*'))
print('****egon***'.lstrip('*'))
print('****egon***'.rstrip('*'))
2、lower,upper
print('AAAbbbb'.lower())
print('AAAbbbb'.upper())

3、startswith,endswith
print('alex is sb'.startswith('alex'))
print('alex is sb'.endswith('sb'))

4、format的三种玩法
print('my name is %s my age is %s' %('egon',18))
print('my name is %s my age is %s' %(18,'egon'))

print('my name is {name} my age is {age} '.format(age=18,name='egon'))

print('my name is {} my age is {} '.format(18,'egon'))
print('my name is {0} my age is {1} '.format(18,'egon'))
print('my name is {1} my age is {0} '.format(18,'egon'))

5、split,rsplit
msg='a:b:c:d:e'
print(msg.split(':',1))
print(msg.rsplit(':',1))

6、join
msg='a:b:c:d:e'
list1=msg.split(':')
msg1=':'.join(list1)
print(msg1)

info='egon:123:male'
list1=info.split(':')
print(list1)

print(':'.join(list1))

7、replace
msg='alex is alex alex is hahahaha'
print(msg.replace('alex','SB',1))

8、isdigit
print('123'.isdigit()) # 只能判断纯数字的字符串
print('12.3'.isdigit())

age_of_db=30
inp_age=input('>>>: ').strip()
if inp_age.isdigit():
    inp_age=int(inp_age)
    if inp_age > age_of_db:
        print('too big')
    elif inp_age < age_of_db:
        print('too small')
    else:
        print('you got it')

其他操作1、find,rfind,index,rindex,count
msg='hello worldaa'
print(msg.index('wo'))
print(msg.index('wo',0,3))
print(msg.find('wo',0,3))
print(msg.find('xxxxxxx'))
print(msg.index('xxxxxxx'))
print(msg.count('l'))

2、center,ljust,rjust,zfill
name=input('>>: ').strip()
print('egon'.center(50,'='))
print(('%s' %name).center(50,'-'))

print('egon'.ljust(50,'='))
print('egon'.rjust(50,'='))
print('egon'.zfill(50))

3、expandtabs
print('hello	world'.expandtabs(5))

4、captalize,swapcase,title
print('hello world'.capitalize())
print('Hello world'.swapcase())
print('Hello world'.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='四' #中文数字
num4='Ⅳ' #罗马数字

isdigit: bytes,str
print(num1.isdigit())
print(num2.isdigit())
print(num3.isdigit())
print(num4.isdigit())

isdecimal:str
print(num2.isdecimal())
print(num3.isdecimal())
print(num4.isdecimal())

isnumberic:str,中文罗马
print(num2.isnumeric())
print(num3.isnumeric())
print(num4.isnumeric())

6、is其他
print('aaasdfaA'.isalpha()) # 纯字母组成的字符串
print('aaasdfaA123'.isalnum()) # 字母或数字组成
print('aaasdfaA'.isalnum()) # 字母或数字组成