python中字符串用法_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='asdfs123t523fgbdf'

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='sdfgdfgt'

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='helwloasnvxcwaewcnafgasdfs'

b=a.splitlines()

c=a.splitlines(True)

print(b)

print(c)

—>[‘helwloas', ‘vxcwaewc', ‘afgasdfs']

—>[‘helwloasn', ‘vxcwaewcn', ‘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