Python字符串的内置方法

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如何查看字符串有哪些内置方法？
我们可以先创建一个类型为字符串的变量，然后查看该变量的类型。

然后用dir()方法查看字符串的内置方法有哪些。最后可以用help()查看各个内置方法的用法

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>>> string='hello' >>> type(string) <type 'str'> >>> dir(str) ['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs',   'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower',   'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip',   'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition',   'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip',   'swapcase', 'title', 'translate', 'upper', 'zfill']

以上就是字符串所有的内置方法。

常用的字符串方法：

capitalize():  首字母大写

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>>> string="asdf"   >>> string.capitalize()   'Asdf'

center(长度，填充符号)：

  输出指定长度的字符串，并且将目标字符串居中，两边以指定的符号填充

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string="asdf"      >>> string.center(10,'*')      ‘***asdf***'

count(‘字符串’，开始下标，结束下标) ：

查看子序列的个数，或者说查看某个字符的个数

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>>> name="asdfsdfsdfasdf"        >>> name.count('s')        4         >>> name.count('s',0,9)          3

expandtabs(空格个数)：

将tab转换成空格，可以指定转换成多格式空格，默认一个tab转换成8个空格

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>>> name='ze\tng' >>> name.expandtabs() 'ze      ng' >>> name.expandtabs(1) 'ze ng’

find() :

寻找第一个被匹配到的子序列的下标，如果没有找到，则返回-1

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>>> string 'asdf' >>> string.find('s') 1 >>> string.find('e') -1

format() :

字符串格式化

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>>> string = "I am {0},age {1}" >>> string.format('zenge',28) 'I am zenge,age 28'    还可以这样： >>> string = "I am {ss},age {dd}" >>> string.format(ss='zenge',dd=28) 'I am zenge,age 28’ ##第二种方法相比较于第一种方法好处是，传值的时候不需要按照顺序传

      列表传参

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>>> list=[‘zeng',28] >>> name="I am {0},age {1}"    >>> name.format(*list)      'I am zeng,age 28’

     字典传参

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>>> dict={'ss':'zeng','dd':28} >>> name="I am {ss},age {dd}" >>> name.format(**dict)       'I am zeng,age 28'

index():  

查找指定字符的下标，和find差不多，区别在于如果要查找的字符不存在，那么find返回-1，而index则会报错   

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>>> string = "asddfasd" >>> string.index(d) >>> string.index('d') 2

isalnum()：

检查字符串是否为字母和数字，返回值为布尔型   

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>>> name="曾"    >>> name.isalnum() False

islower():

检查字符串是否全都是小写，返回值为布尔型，对应的是isupper()      

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>>> name="asdfasA" >>> name.islower() False

isdigit():

检查字符串是否全部为数字

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>>> num='12323' >>> num.isdigit() True >>> num='123234hehe' >>> num.isdigit() False

isspace()：

检查字符串是否全部为空格

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>>> name = '   ' >>> name.isspace() True >>> name = '  1' >>> name.isspace() False

istitle() :  

检查字符串是否为标题（标题的特点是首字母大写）

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>>> name= "alex sb" >>> name.istitle() False

titie() :  

将字符串转换成标题,  标题格式就是首字母大写

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>>> name= "alex sb" >>> name.title() 'Alex Sb’

join() :  

将列表中的元素用符号连接起来组成字符串

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>>> list=["zeng",'28'] >>> '_'.join(list) 'zeng_28'

ljust(宽度，填充符号) :  

内容左对齐   右对齐为rjust()，与center()对应

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>>> name=“asdasd" >>> name.ljust(20,'*') 'asdasd**************'

upper() ：  

字符串由小写变成大写, 与之相反的是lower() ,大写变成小写

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>>> name 'asdasd' >>> name.upper() 'ASDASD'

swapcase() :  

大小写转换，大写的转换成小写，小写的转换成大写

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>>> name="aaaBBB" >>> name.swapcase() 'AAAbbb'

partition() ：

将字符串按照指定的字符或者符号分割成前中后三部分

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>>> name="Hello world" >>> name.partition('ll') ('He', 'll', 'o world’)

replace(old，new)：

替换 ,注意字符中所有满足条件的都会被替换

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'Hello world' >>> name.replace('ll','LL') 'HeLLo world'

split()

将字符串以某个字符分割，分割后的结果为列表

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>>> name = "hello,zeng" >>> name.split(',') ['hello', 'zeng']

strip()

删除字符串中指定的字符，例如删除空格，rstrip()方法是删除字符串右边的指定字符，lstrip()方法是删除字符串左边的指定字符

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>>> name = '  zeng ' >>> name.strip('') '  zeng ' >>> name.strip(' ') 'zeng' >>> name.rstrip(' ') '  zeng' >>> name.lstrip(' ') 'zeng '

使用help()方法查看字符串所有内置方法的详细信息和用法

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|  Methods defined here: |   |  __add__(...) |      x.__add__(y) <==> x+y |   |  __contains__(...) |      x.__contains__(y) <==> y in x |   |  __eq__(...) |      x.__eq__(y) <==> x==y |   |  __format__(...) |      S.__format__(format_spec) -> string |       |      Return a formatted version of S as described by format_spec. |   |  __ge__(...) |      x.__ge__(y) <==> x>=y |   |  __getattribute__(...) |      x.__getattribute__('name') <==> x.name |   |  __getitem__(...) |      x.__getitem__(y) <==> x[y] |   |  __getnewargs__(...) |   |  __getslice__(...) |      x.__getslice__(i, j) <==> x[i:j] |       |      Use of negative indices is not supported. |   |  __gt__(...) |      x.__gt__(y) <==> x>y |   |  __hash__(...) |      x.__hash__() <==> hash(x) |   |  __le__(...) |      x.__le__(y) <==> x<=y |   |  __len__(...) |      x.__len__() <==> len(x) |   |  __lt__(...) |      x.__lt__(y) <==> x<y |   |  __mod__(...) |      x.__mod__(y) <==> x%y |   |  __mul__(...) |      x.__mul__(n) <==> x*n |   |  __ne__(...) |      x.__ne__(y) <==> x!=y |   |  __repr__(...) |      x.__repr__() <==> repr(x) |   |  __rmod__(...) |      x.__rmod__(y) <==> y%x |   |  __rmul__(...) |      x.__rmul__(n) <==> n*x |   |  __sizeof__(...) |      S.__sizeof__() -> size of S in memory, in bytes |   |  __str__(...) |      x.__str__() <==> str(x) |   |  capitalize(...) |      S.capitalize() -> string |       |      Return a copy of the string S with only its first character |      capitalized. |   |  center(...) |      S.center(width[, fillchar]) -> string |       |      Return S centered in a string of length width. Padding is |      done using the specified fill character (default is a space) |   |  count(...) |      S.count(sub[, start[, end]]) -> int |       |      Return the number of non-overlapping occurrences of substring sub in |      string S[start:end].  Optional arguments start and end are interpreted |      as in slice notation. |   |  decode(...) |      S.decode([encoding[,errors]]) -> object |       |      Decodes S using the codec registered for encoding. encoding defaults |      to the default encoding. errors may be given to set a different error |      handling scheme. Default is 'strict' meaning that encoding errors raise |      a UnicodeDecodeError. Other possible values are 'ignore' and 'replace' |      as well as any other name registered with codecs.register_error that is |      able to handle UnicodeDecodeErrors. |   |  encode(...) |      S.encode([encoding[,errors]]) -> object |       |      Encodes S using the codec registered for encoding. encoding defaults |      to the default encoding. errors may be given to set a different error |      handling scheme. Default is 'strict' meaning that encoding errors raise |      a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and |      'xmlcharrefreplace' as well as any other name registered with |      codecs.register_error that is able to handle UnicodeEncodeErrors. |   |  endswith(...) |      S.endswith(suffix[, start[, end]]) -> bool |       |      Return True if S ends with the specified suffix, False otherwise. |      With optional start, test S beginning at that position. |      With optional end, stop comparing S at that position. |      suffix can also be a tuple of strings to try. |   |  expandtabs(...) |      S.expandtabs([tabsize]) -> string |       |      Return a copy of S where all tab characters are expanded using spaces. |      If tabsize is not given, a tab size of 8 characters is assumed. |   |  find(...) |      S.find(sub [,start [,end]]) -> int |       |      Return the lowest index in S where substring sub is found, |      such that sub is contained within S[start:end].  Optional |      arguments start and end are interpreted as in slice notation. |       |      Return -1 on failure. |   |  format(...) |      S.format(*args, **kwargs) -> string |       |      Return a formatted version of S, using substitutions from args and kwargs. |      The substitutions are identified by braces ('{' and '}'). |   |  index(...) |      S.index(sub [,start [,end]]) -> int |       |      Like S.find() but raise ValueError when the substring is not found. |   |  isalnum(...) |      S.isalnum() -> bool |       |      Return True if all characters in S are alphanumeric |      and there is at least one character in S, False otherwise. |   |  isalpha(...) |      S.isalpha() -> bool |       |      Return True if all characters in S are alphabetic |      and there is at least one character in S, False otherwise. |   |  isdigit(...) |      S.isdigit() -> bool |       |      Return True if all characters in S are digits |      and there is at least one character in S, False otherwise. |   |  islower(...) |      S.islower() -> bool |       |      Return True if all cased characters in S are lowercase and there is |      at least one cased character in S, False otherwise. |   |  isspace(...) |      S.isspace() -> bool |       |      Return True if all characters in S are whitespace |      and there is at least one character in S, False otherwise. |   |  istitle(...) |      S.istitle() -> bool |       |      Return True if S is a titlecased string and there is at least one |      character in S, i.e. uppercase characters may only follow uncased |      characters and lowercase characters only cased ones. Return False |      otherwise. |   |  isupper(...) |      S.isupper() -> bool |       |      Return True if all cased characters in S are uppercase and there is |      at least one cased character in S, False otherwise. |   |  join(...) |      S.join(iterable) -> string |       |      Return a string which is the concatenation of the strings in the |      iterable.  The separator between elements is S. |   |  ljust(...) |      S.ljust(width[, fillchar]) -> string |       |      Return S left-justified in a string of length width. Padding is |      done using the specified fill character (default is a space). |   |  lower(...) |      S.lower() -> string |       |      Return a copy of the string S converted to lowercase. |   |  lstrip(...) |      S.lstrip([chars]) -> string or unicode |       |      Return a copy of the string S with leading whitespace removed. |      If chars is given and not None, remove characters in chars instead. |      If chars is unicode, S will be converted to unicode before stripping |   |  partition(...) |      S.partition(sep) -> (head, sep, tail) |       |      Search for the separator sep in S, and return the part before it, |      the separator itself, and the part after it.  If the separator is not |      found, return S and two empty strings. |   |  replace(...) |      S.replace(old, new[, count]) -> string |       |      Return a copy of string S with all occurrences of substring |      old replaced by new.  If the optional argument count is |      given, only the first count occurrences are replaced. |   |  rfind(...) |      S.rfind(sub [,start [,end]]) -> int |       |      Return the highest index in S where substring sub is found, |      such that sub is contained within S[start:end].  Optional |      arguments start and end are interpreted as in slice notation. |       |      Return -1 on failure. |   |  rindex(...) |      S.rindex(sub [,start [,end]]) -> int |       |      Like S.rfind() but raise ValueError when the substring is not found. |   |  rjust(...) |      S.rjust(width[, fillchar]) -> string |       |      Return S right-justified in a string of length width. Padding is |      done using the specified fill character (default is a space) |   |  rpartition(...) |      S.rpartition(sep) -> (head, sep, tail) |       |      Search for the separator sep in S, starting at the end of S, and return |      the part before it, the separator itself, and the part after it.  If the |      separator is not found, return two empty strings and S. |   |  rsplit(...) |      S.rsplit([sep [,maxsplit]]) -> list of strings |       |      Return a list of the words in the string S, using sep as the |      delimiter string, starting at the end of the string and working |      to the front.  If maxsplit is given, at most maxsplit splits are |      done. If sep is not specified or is None, any whitespace string |      is a separator. |   |  rstrip(...) |      S.rstrip([chars]) -> string or unicode |       |      Return a copy of the string S with trailing whitespace removed. |      If chars is given and not None, remove characters in chars instead. |      If chars is unicode, S will be converted to unicode before stripping |   |  split(...) |      S.split([sep [,maxsplit]]) -> list of strings |       |      Return a list of the words in the string S, using sep as the |      delimiter string.  If maxsplit is given, at most maxsplit |      splits are done. If sep is not specified or is None, any |      whitespace string is a separator and empty strings are removed |      from the result. |   |  splitlines(...) |      S.splitlines(keepends=False) -> list of strings |       |      Return a list of the lines in S, breaking at line boundaries. |      Line breaks are not included in the resulting list unless keepends |      is given and true. |   |  startswith(...) |      S.startswith(prefix[, start[, end]]) -> bool |       |      Return True if S starts with the specified prefix, False otherwise. |      With optional start, test S beginning at that position. |      With optional end, stop comparing S at that position. |      prefix can also be a tuple of strings to try. |   |  strip(...) |      S.strip([chars]) -> string or unicode |       |      Return a copy of the string S with leading and trailing |      whitespace removed. |      If chars is given and not None, remove characters in chars instead. |      If chars is unicode, S will be converted to unicode before stripping |   |  swapcase(...) |      S.swapcase() -> string |       |      Return a copy of the string S with uppercase characters |      converted to lowercase and vice versa. |   |  title(...) |      S.title() -> string |       |      Return a titlecased version of S, i.e. words start with uppercase |      characters, all remaining cased characters have lowercase. |   |  translate(...) |      S.translate(table [,deletechars]) -> string |       |      Return a copy of the string S, where all characters occurring |      in the optional argument deletechars are removed, and the |      remaining characters have been mapped through the given |      translation table, which must be a string of length 256 or None. |      If the table argument is None, no translation is applied and |      the operation simply removes the characters in deletechars. |   |  upper(...) |      S.upper() -> string |       |      Return a copy of the string S converted to uppercase. |   |  zfill(...) |      S.zfill(width) -> string |       |      Pad a numeric string S with zeros on the left, to fill a field |      of the specified width.  The string S is never truncated. |   |  ---------------------------------------------------------------------- |  Data and other attributes defined here: |   |  __new__ = <built-in method __new__ of type object> |      T.__new__(S, ...) -> a new object with type S, a subtype of T