【Python3】字符串操作

name='my name is jack'
name.capitalize()  #首字母大写
name.casefold()   #大写全部变小写
name.center(50,"-")  #输出 '-------------my name is jack--------------'，共50个字符
name.count('a') #统计a出现次数
name.encode()  #将字符串编码成bytes格式
name.endswith("k")  #判断字符串是否以a结尾
"my\tname".expandtabs(10) #输出'my      name'， 将\t转换成多长的空格 
name.find('jack')  #查找jack,找到返回其索引(首位置)，找不到返回-1
name.rfind('a')　　#查找最右边的'a'

format :
    >>> msg = "my name is {}, and age is {}"
    >>> msg.format("jack",22)
    'my name is jack, and age is 22'
    >>> msg = "my name is {1}, and age is {0}"
    >>> msg.format(22,"jack")
    'my name is jack, and age is 22'
    >>> msg = "my name is {name}, and age is {age}"
    >>> msg.format(name="jack",age=22)
    'my name is jack, and age is 22'
format_map
    >>> msg.format_map({'name':'alex','age':22})
    'my name is alex, and age is 22'

'banana'.index('a')  #返回a所在字符串的索引  
'9aA'.isalnum()   True #是否是英文或数字
'9aA!'.isalnum()　　False
'9aA'.isalpha()　　True #是否是英文
'1B'.isdecimal()　　True #是否是16进制
'9'.isdigit() #是否整数
'abc'.islower()　　True #是否全小写
'ABC'.isupper()　　True #是否全大写
'123'.isnumeric()  True #是否纯数字
'2A'.isnumeric()　　False 
驱动程序.isprintable()　　False
' '.isspace #是否空格
'My Name Is Jack'.istitle()　　True #每个单词首字母是否大写
'My name is jack'.istitle()　　False

>>>"|".join(['sandra','jack','happy'])
'sandra|jack|happy'

maketrans #定义字符转换规则,和translate一起用
    >>> intab = "aeiou"  #This is the string having actual characters. 
    >>> outtab = "12345" #This is the string having corresponding mapping character
    >>> transtab = str.maketrans(intab, outtab)
    >>> str = "this is string example"
    >>> str.translate(transtab)
    'th3s 3s str3ng 2x1mpl2'

msg.partition('is')   输出 ('my name ', 'is', ' {name}, and age is {age}') 

>>> "jack, chinese name is xu".replace("jack","sandra",1) #默认全部替换
'sandra, chinese name is xu'

msg.swapcase 大小写互换

>>> msg.zfill(50) #'0'填充
'00000my name is {name}, and age is {age}'

>>> 'Hello World'.ljust(50,"-")
'Hello World-----------------------------'
>>> 'Hello World'.rjust(50,"-")
'-----------------------------Hello World'

>>>'Jack'.lower() #改小写
'jack'
>>>'jACK'　　#改大写
'JACK'

>>> b="name" 
>>> b.isidentifier() #检测一段字符串可否被当作标志符，即是否符合变量命名规则
True

>>>'\n jack\n'.strip() #去掉两端的空格和换行
jack
>>>'\njack'.lstrip()
>>>'jack\n'.rstrip()

>>>'1+2+3+4+5'.split('+')　　#得到列表
['1','2','3','4','5']
>>>'1+2+3\n+4+5'.splitlines()　　#按换行符分，得到列表
['1+2+3','+4+5']