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