python中字符串内置函数的用法总结

capitalize（） 首字母大写

a='someword'
 b=a.capitalize()
 print(b)
 —>Someword

casefold()&lower() 所有字母变小写，casefold可将未知字符便小写

a='someWORD'
  b=a.casefold()
  print(b)
  c=a.lower()
  print(c)
  —>someword
  —>someword

center(width,fillchar=None) 设置宽度，并将内容居中，空白未知填充，一个字符

a='someword'
  b=a.center(30,'*')
  print(b)

count(sub,start=None,end=None) 去字符串中寻找，寻找子序列的出现次数，可指定起止点

a='somewordsomeword'
 b=a.count(‘or')
 print(b)
 —>2

startswith(suffix,start=None,end=None)&endswith(suffix,start=None,end=None) 是否以XX开始/结束，可指定起止点

a='somewordsomeword'
  b=a.startswith(‘sa')
  c=a.endswith(‘ord')
  print(b)
  print(c)
  —>False
  —>True

find(sub,start=None,end=None) 寻找指定字符或字符串，并返回第一个位置，找不到返回-1，可指定起止点

a='somewordsomeword'
  b=a.find(‘me')
  print(b)
  —>2

format() 格式化，将一个字符串中的占位符替换为指定的值

test='I am {name},age {a}'
  v=test.format(name='alex',a=19)
  print(v)
  —>i am alex,age 19

format_map() 格式化，传入的值

test='iam{name},age{a}'
  v=test.format_map({“name”:'alex',”a”:19})
  print(v)
  —>i am alex,age 19

isalnum() 字符串中是否只包含字母和数字

a='asdfs123*'
  b=a.isalnum()
  print(b)
  —>False

expandtabs(tabsize=number) 将字符串以number分割，并将tab补入

a='asdfs123\t523fgbdf'
 b=a.expandtabs(5)
 print(b)
 —>asdfs123 523fgbdf

isalpha() 字符串中是只包含字母

a='asdfsfgbdf'
 b=a.isalpha()
 print(b)
 —>True

isdecimal()&isdigit()&isnumeric() 字符串中是只包含数字，isdigit更为强大，isnumeric还可识别中文

a='132132②二'
  b=a.isdecimal()
  c=a.isdigit()
  d=a.isnumeric()
  print(b)
  print(c)
  print(d)
  —>False
  —>False
  —>True

isprintable() 是否存在不可显示的字符如换行符

a='sdfgdfg\t'
 b=a.isprintable()
 print(b)
 —>False

isspace() 判断是否全部为空格

a='dsvsdv'
  b=a.isspace()
  print(b)
  —>False

istitle()&title() 判断是否为标题，即首字母大写&变为标题

a='follow uncased characters and lowercase characters only cased ones'
  b=a.istitle()
  print(b)
  c=a.title()
  print(c)
  —>False
  —>Follow Uncased Characters And Lowercase Characters Only Cased Ones

join(iterable) 将字符串中的每个元素按照指定分隔符进行拼接

a='一二三四五六七'
  print(a)
  b='*'
  c=b.join(a)
  print(c)
  —>一二三四五六七
  —>一二三四五六七

ljust(width,fillchar=None)&rjust(width,fillchar=None) 向右/左填充字符

a='hello'
 b=a.ljust(20,'*')
 c=a.rjust(20,'*')
 print(b)
 print(c)
 —>hello***************
 —>***************hello

islower()&lower() 判断是是否为全小写&变为全部小写

a='Hello'
  b=a.islower()
  c=a.lower()
  print(b,c)
  —>False hello

isupper()&c=a.upper() 判断是是否为全大写&变为全部大写

a='Hello'
  b=a.isupper()
  c=a.upper()
  print(b,c)
  —>False HELLO

lstrip(chars=None)&rstrip(chars=None)&strip(chars=None) 去除字符串左边/右边/两边的字符串，默认空格，换行等

a='Hello'
  b=a.lstrip()
  c=a.rstrip()
  d=a.strip()
  print(b)
  print(c)
  print(d)
  —>Hello
  —> Hello
  —>Hello

maketrans(*args,**kwargs)&translate(table) 按maketrans对应关系将translate中的字符串进行替换

a='asdgfrfbcvzxrentas'
  b=str.maketrans(‘xdsa','1234')
  c=a.translate(b)
  print(c)
  —> 432gfrfbcvz1rent43

partition(sep)&rpartition(sep) 将字符串按指定字符分割成3段/或从右开始

a='helwloasvxcwaewc'
  b=a.partition(‘w')
  c=a.rpartition(‘w')
  print(b)
  print(c)
  —>(‘hel', ‘w', ‘loasvxcwaewc')
  —>(‘helwloasvxcwae', ‘w', ‘c')

split(sep=None,maxsplit=-1)&rsplit(sep=None,maxsplit=-1) 将字符串按指定字符串分割，分割后不保留

a='helwloasvxcwaewc'
  b=a.split(‘w',2)
  c=a.rsplit(‘w')
  print(b)
  print(c)
  —>[‘hel', ‘loasvxc', ‘aewc']
  —>[‘hel', ‘loasvxc', ‘ae', ‘c']

splitlines(keepends=None) 按照换行符进行分割，带true参数保留换行符

a='helwloas\nvxcwaewc\nafgasdfs'
  b=a.splitlines()
  c=a.splitlines(True)
  print(b)
  print(c)
  —>[‘helwloas', ‘vxcwaewc', ‘afgasdfs']
  —>[‘helwloas\n', ‘vxcwaewc\n', ‘afgasdfs']

startswith(prefix,start=None,end=None)&endswith(prefix,start=None,end=None) 判断字符串是否以指定字符开始/结束，可指定起止点

a='aefsfsfeeav'
  b=a.startswith(‘ae')
  c=a.endswith(‘av',1,9)
  print(b)
  print(c)
  True
  —>False

swapcase() 小写转变为大写

a='aefsfsfeeav'
  b=a.swapcase()
  print(b)
  —>AEFSFSFEEAV