New-Python-数据类型、字符编码、文件处理

一、字符串的一些应用：

#strip
name='*egon**'
print(name.strip('*'))
print(name.lstrip('*'))
print(name.rstrip('*'))

#startswith,endswith
name='alex_SB'
print(name.endswith('SB'))
print(name.startswith('alex'))

#replace
name='alex say :i have one tesla,my name is alex'
print(name.replace('alex','SB',1))

#format的三种玩法
res='{} {} {}'.format('egon',18,'male')
res='{1} {0} {1}'.format('egon',18,'male')
res='{name} {age} {sex}'.format(sex='male',name='egon',age=18)

#find,rfind,index,rindex,count
name='egon say hello'
print(name.find('o',1,3)) #顾头不顾尾,找不到则返回-1不会报错,找到了则显示索引
# print(name.index('e',2,4)) #同上,但是找不到会报错
print(name.count('e',1,3)) #顾头不顾尾,如果不指定范围则查找所有


#split
name='root:x:0:0::/root:/bin/bash'
print(name.split(':')) #默认分隔符为空格
name='C:/a/b/c/d.txt' #只想拿到顶级目录
print(name.split('/',1))

name='a|b|c'
print(name.rsplit('|',1)) #从右开始切分


#join
tag=' '
print(tag.join(['egon','say','hello','world'])) #可迭代对象必须都是字符串

#center,ljust,rjust,zfill
name='egon'
print(name.center(30,'-'))
print(name.ljust(30,'*'))
print(name.rjust(30,'*'))
print(name.zfill(50)) #用0填充


#expandtabs
name='egon	hello'
print(name)
print(name.expandtabs(1))

#lower,upper
name='egon'
print(name.lower())
print(name.upper())


#captalize,swapcase,title
print(name.capitalize()) #首字母大写
print(name.swapcase()) #大小写翻转
msg='egon say hi'
print(msg.title()) #每个单词的首字母大写

#is数字系列
#在python3中
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

#isdigt:bytes,unicode
print(num1.isdigit()) #True
print(num2.isdigit()) #True
print(num3.isdigit()) #False
print(num4.isdigit()) #False


#isdecimal:uncicode
#bytes类型无isdecimal方法
print(num2.isdecimal()) #True
print(num3.isdecimal()) #False
print(num4.isdecimal()) #False

#isnumberic:unicode,中文数字,罗马数字
#bytes类型无isnumberic方法
print(num2.isnumeric()) #True
print(num3.isnumeric()) #True
print(num4.isnumeric()) #True


#三者不能判断浮点数
num5='4.3'
print(num5.isdigit()) 
print(num5.isdecimal())
print(num5.isnumeric())
'''
总结:
    最常用的是isdigit,可以判断bytes和unicode类型,这也是最常见的数字应用场景
    如果要判断中文数字或罗马数字,则需要用到isnumeric
'''

#is其他
print('===>')
name='egon123'
print(name.isalnum()) #字符串由字母或数字组成
print(name.isalpha()) #字符串只由字母组成

print(name.isidentifier())
print(name.islower())
print(name.isupper())
print(name.isspace())
print(name.istitle())

#请输出 name 变量对应的值的后 2 个字符?

#获取子序列,去掉最后一个字符。如: oldboy 则获取 oldbo。
name = " aleX"

print(name[-2:])    #空代表取到最后，或从最一开始取
print(name[:-1])

二、列表功能

my_girl_friends=['alex','wupeiqi','yuanhao',4,5] #本质my_girl_friends=list([...])
print(my_girl_friends[2])
print(my_girl_friends[-1])
my_girl_friends[5]='6号'   #增加
print(id(my_girl_friends))
my_girl_friends[0]='SB'    #更改
print(my_girl_friends)
print(id(my_girl_friends))   #id不变

print(my_girl_friends[0:2])   #截取
print(my_girl_friends[0:2:1])
print(my_girl_friends[0:4])
print(my_girl_friends[0:4:2])

print(len(my_girl_friends))

print('alex' in my_girl_friends)
print(5 in my_girl_friends)

my_girl_friends.append('6号')
del my_girl_friends[2]    #通用删除法
print(my_girl_friends)

my_girl_friends.remove('yuanhao')
print(my_girl_friends)

my_girl_friends.pop()     #拿走一个值，而不是单纯的删除
my_girl_friends.pop()
my_girl_friends.pop(1)      #按照索引去删
print(my_girl_friends.pop(1))
print(my_girl_friends)
res=my_girl_friends.pop(1)
print(res)

my_girl_friends=['alex','wupeiqi','yuanhao',4,'alex',5] #本质my_girl_friends=list([...])
my_girl_friends.insert(0,'sb_alex')
print(my_girl_friends)
my_girl_friends.insert(2,'yh')
my_girl_friends.extend([0,1,2,3,4,5])
print(my_girl_friends)

print(my_girl_friends.count('alex'))

my_girl_friends.clear()
print(my_girl_friends)

l=my_girl_friends.copy()
print(l)

my_girl_friends.reverse()
print(my_girl_friends)

l=[1,2,6,4,-1,3]
l.sort()
l.sort(reverse=True)
print(l)

append,pop:队列，先进先出
l=[]
l.append('first')
l.append('second')
l.append('third')
print(l)
print(l.pop(0))
print(l.pop(0))
print(l.pop(0))

insert,pop:堆栈，先进后出
l=[]
l.insert(0,'first')
l.insert(0,'second')
l.insert(0,'third')
print(l)
print(l.pop(0))
print(l.pop(0))
print(l.pop(0))

l1=[]
l1.insert(0,'first')
l1.insert(0,'second')
l1.insert(0,'third')
print(l1)
print(l1.pop(0))
print(l1.pop(0))
print(l1.pop(0))