python基础知识-字符串

字符串：

赋值方法

a = 'name'

a = str('name')

字符串的方法：

 #!/usr/bin/env python
 class str(object):
     """
     str(object='') -> str
     str(bytes_or_buffer[, encoding[, errors]]) -> str

     Create a new string object from the given object. If encoding or
     errors is specified, then the object must expose a data buffer
     that will be decoded using the given encoding and error handler.
     Otherwise, returns the result of object.__str__() (if defined)
     or repr(object).
     encoding defaults to sys.getdefaultencoding().
     errors defaults to 'strict'.
     """
     def capitalize(self): # real signature unknown; restored from __doc__
         '''首字母大写'''
         """
         S.capitalize() -> str

         Return a capitalized version of S, i.e. make the first character
         have upper case and the rest lower case.
         """
         return ""

     def casefold(self): # real signature unknown; restored from __doc__
         '''全部转换为小写'''
         """
         S.casefold() -> str

         Return a version of S suitable for caseless comparisons.
         """
         return ""

     def center(self, width, fillchar=None): # real signature unknown; restored from __doc__
         '''内容居中，width：总长度，fillchar：空白处填充内容，默认无'''
         """
         S.center(width[, fillchar]) -> str

         Return S centered in a string of length width. Padding is
         done using the specified fill character (default is a space)
         """
         return ""

     def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
         '''子序列个数'''
         """
         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.
         """
         return 0

     def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__
         '''编码，针对unicode'''
         """
         S.encode(encoding='utf-8', errors='strict') -> bytes

         Encode S using the codec registered for encoding. Default encoding
         is 'utf-8'. 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 can handle UnicodeEncodeErrors.
         """
         return b""

     def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__
         '''判断是否以特定值结尾，也可以是一个元组。如果是则为真（True）'''
         """
         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.
         """
         return False

     def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__
         '''将一个tab键转换为空格，默认为8个空格'''
         """
         S.expandtabs(tabsize=8) -> str

         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.
         """
         return ""

     def find(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
         '''寻找子序列的位置，如果没有找到则返回 -1，只查找一次找到及返回 '''
         """
         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.
         """
         return 0

     def format(*args, **kwargs): # known special case of str.format
         '''字符串格式转化'''
         """
         S.format(*args, **kwargs) -> str

         Return a formatted version of S, using substitutions from args and kwargs.
         The substitutions are identified by braces ('{' and '}').
         """
         pass

     def format_map(self, mapping): # real signature unknown; restored from __doc__
         """
         S.format_map(mapping) -> str

         Return a formatted version of S, using substitutions from mapping.
         The substitutions are identified by braces ('{' and '}').
         """
         return ""

     def index(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
         '''子序列的位置，如果没有找到返回错误'''
         """
         S.index(sub[, start[, end]]) -> int

         Like S.find() but raise ValueError when the substring is not found.
         """
         return 0

     def isalnum(self): # real signature unknown; restored from __doc__
         '''是否是字母或数字'''
         """
         S.isalnum() -> bool

         Return True if all characters in S are alphanumeric
         and there is at least one character in S, False otherwise.
         """
         return False

     def isalpha(self): # real signature unknown; restored from __doc__
         '''是否所有字符都为字母'''
         """
         S.isalpha() -> bool

         Return True if all characters in S are alphabetic
         and there is at least one character in S, False otherwise.
         """
         return False

     def isdecimal(self): # real signature unknown; restored from __doc__
         '''是否为十进制数'''
         """
         S.isdecimal() -> bool

         Return True if there are only decimal characters in S,
         False otherwise.
         """
         return False

     def isdigit(self): # real signature unknown; restored from __doc__
         '''是否所有字符都为数字'''
         """
         S.isdigit() -> bool

         Return True if all characters in S are digits
         and there is at least one character in S, False otherwise.
         """
         return False

     def isidentifier(self): # real signature unknown; restored from __doc__
         '''是否为有效标识符'''
         """
         S.isidentifier() -> bool

         Return True if S is a valid identifier according
         to the language definition.

         Use keyword.iskeyword() to test for reserved identifiers
         such as "def" and "class".
         """
         return False

     def islower(self): # real signature unknown; restored from __doc__
         '''是否所有字符都为小写'''
         """
         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.
         """
         return False

     def isnumeric(self): # real signature unknown; restored from __doc__
         '''是否只有数字'''
         """
         S.isnumeric() -> bool

         Return True if there are only numeric characters in S,
         False otherwise.
         """
         return False

     def isprintable(self): # real signature unknown; restored from __doc__
         '''内容是否都是可见的字符，不可见的包括tab键，换行符。空格为可见字符'''
         """
         S.isprintable() -> bool

         Return True if all characters in S are considered
         printable in repr() or S is empty, False otherwise.
         """
         return False

     def isspace(self): # real signature unknown; restored from __doc__
         '''是否只有空格组成'''
         """
         S.isspace() -> bool

         Return True if all characters in S are whitespace
         and there is at least one character in S, False otherwise.
         """
         return False

     def istitle(self): # real signature unknown; restored from __doc__
         '''是否为标题化的'''
         """
         S.istitle() -> bool

         Return True if S is a titlecased string and there is at least one
         character in S, i.e. upper- and titlecase characters may only
         follow uncased characters and lowercase characters only cased ones.
         Return False otherwise.
         """
         return False

     def isupper(self): # real signature unknown; restored from __doc__
         '''是否都为大写字母'''
         """
         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.
         """
         return False

     def join(self, iterable): # real signature unknown; restored from __doc__
         '''连接，以S作为分隔符，把所有iterable中的元素合并成一个新的字符串'''
         """
         S.join(iterable) -> str

         Return a string which is the concatenation of the strings in the
         iterable.  The separator between elements is S.
         """
         return ""

     def ljust(self, width, fillchar=None): # real signature unknown; restored from __doc__
         '''左对齐，width 字符串的长度，右侧以fillchar填充，默认为空'''
         """
         S.ljust(width[, fillchar]) -> str

         Return S left-justified in a Unicode string of length width. Padding is
         done using the specified fill character (default is a space).
         """
         return ""

     def lower(self): # real signature unknown; restored from __doc__
         '''所有字母大写变小写，返回一个小写的副本'''
         """
         S.lower() -> str

         Return a copy of the string S converted to lowercase.
         """
         return ""

     def lstrip(self, chars=None): # real signature unknown; restored from __doc__
         '''去除左侧空白'''
         """
         S.lstrip([chars]) -> str

         Return a copy of the string S with leading whitespace removed.
         If chars is given and not None, remove characters in chars instead.
         """
         return ""

     def maketrans(self, *args, **kwargs): # real signature unknown
         """
         Return a translation table usable for str.translate().

         If there is only one argument, it must be a dictionary mapping Unicode
         ordinals (integers) or characters to Unicode ordinals, strings or None.
         Character keys will be then converted to ordinals.
         If there are two arguments, they must be strings of equal length, and
         in the resulting dictionary, each character in x will be mapped to the
         character at the same position in y. If there is a third argument, it
         must be a string, whose characters will be mapped to None in the result.
         """
         pass

     def partition(self, sep): # real signature unknown; restored from __doc__
         '''分割，把字符以sep分割为 前 中 后 三个部分'''
         """
         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.
         """
         pass

     def replace(self, old, new, count=None): # real signature unknown; restored from __doc__
         '''替换，old替换为new，可以指定次数（count）'''
         """
         S.replace(old, new[, count]) -> str

         Return a copy of S with all occurrences of substring
         old replaced by new.  If the optional argument count is
         given, only the first count occurrences are replaced.
         """
         return ""
 ###########################################################
 #所有以r开头和上面一样的方法，都和上面反方向（即从右到左）#
 ###########################################################
     def rfind(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
         """
         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.
         """
         return 0

     def rindex(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
         """
         S.rindex(sub[, start[, end]]) -> int

         Like S.rfind() but raise ValueError when the substring is not found.
         """
         return 0

     def rjust(self, width, fillchar=None): # real signature unknown; restored from __doc__
         """
         S.rjust(width[, fillchar]) -> str

         Return S right-justified in a string of length width. Padding is
         done using the specified fill character (default is a space).
         """
         return ""

     def rpartition(self, sep): # real signature unknown; restored from __doc__
         """
         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.
         """
         pass

     def rsplit(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
         """
         S.rsplit(sep=None, maxsplit=-1) -> list of strings

         Return a list of the words in 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, any whitespace string
         is a separator.
         """
         return []

     def rstrip(self, chars=None): # real signature unknown; restored from __doc__
         """
         S.rstrip([chars]) -> str

         Return a copy of the string S with trailing whitespace removed.
         If chars is given and not None, remove characters in chars instead.
         """
         return ""

     def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
         '''分割，以什么分割，maxsplit分割次数'''
         """
         S.split(sep=None, maxsplit=-1) -> list of strings

         Return a list of the words in 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.
         """
         return []

     def splitlines(self, keepends=None): # real signature unknown; restored from __doc__
         '''根据换行符分割'''
         """
         S.splitlines([keepends]) -> 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.
         """
         return []

     def startswith(self, prefix, start=None, end=None): # real signature unknown; restored from __doc__
         '''是否以self起始，可以指定开始和结束位置'''
         """
         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.
         """
         return False

     def strip(self, chars=None): # real signature unknown; restored from __doc__
         '''移除两边空白'''
         """
         S.strip([chars]) -> str

         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.
         """
         return ""

     def swapcase(self): # real signature unknown; restored from __doc__
         '''大小写反转'''
         """
         S.swapcase() -> str

         Return a copy of S with uppercase characters converted to lowercase
         and vice versa.
         """
         return ""

     def title(self): # real signature unknown; restored from __doc__
         '''标题化，即首字母大写其余字母为小写'''
         """
         S.title() -> str

         Return a titlecased version of S, i.e. words start with title case
         characters, all remaining cased characters have lower case.
         """
         return ""

     def translate(self, table): # real signature unknown; restored from __doc__
         '''转换，需要做一个对应表，删除的放到最后面'''
         """
         S.translate(table) -> str

         Return a copy of the string S in which each character has been mapped
         through the given translation table. The table must implement
         lookup/indexing via __getitem__, for instance a dictionary or list,
         mapping Unicode ordinals to Unicode ordinals, strings, or None. If
         this operation raises LookupError, the character is left untouched.
         Characters mapped to None are deleted.
         """
         return ""

     def upper(self): # real signature unknown; restored from __doc__
         '''小写字母转换为大写'''
         """
         S.upper() -> str

         Return a copy of S converted to uppercase.
         """
         return ""

     def zfill(self, width): # real signature unknown; restored from __doc__
         '''返回width长度的字符串，原字符串右对齐，前面填充 0 '''
         """
         S.zfill(width) -> str

         Pad a numeric string S with zeros on the left, to fill a field
         of the specified width. The string S is never truncated.
         """
         return ""

str

示例：

####

capitalize()

>>> name = 'binges wang'

>>> name.capitalize()

'Binges wang'

####

casefold()

>>> name = 'Binges Wang'

>>> name.casefold()

'binges wang'

####

center()

>>> name = 'binges'

>>> name.center(10)

'  binges  '

>>> name.center(10,'#')

'##binges##'

####

endswith()

>>> name = 'binges'

>>> name.endswith('s')

True

>>> name.endswith('es')

True

>>> name.endswith('ed')

False

####

find()

>>> name = 'binges wang'

>>> name.find('s')

5

>>> name.find('x')

-1

>>> name.find('g')

3

>>> name.find('an')

8

####

index()

>>> name = 'binges wang'

>>> name.index('a')

8

>>> name.index('s')

5

>>> name.index('an')

8

>>> name.index('x')

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: substring not found

####

isalnum()

>>> name = 'binges'

>>> name.isalnum()

True

>>> name = 'binges 12'

>>> name.isalnum()

False

>>> name = 'binges12'

>>> name.isalnum()

True

>>> age = '12'

>>> age.isalnum()

True

####

isalpha()

>>> name = 'binges12'

>>> name.isalpha()

False

>>> name = 'binges wang'

>>> name.isalpha()

False

>>> name = 'binges'

>>> name.isalpha()

True

####

isdigit()

>>> age = '23'

>>> age.isdigit()

True

>>> age = '23 '

>>> age.isdigit()

False

>>> age = '23.5'

>>> age.isdigit()

False

####

isidentifier()

>>> name = 'binges wang'

>>> name.isidentifier()

False

>>> name = 'binges'

>>> name.isidentifier()

True

####

islower()

>>> name = 'binges'

>>> name.islower()

True

>>> name = 'binges wang'

>>> name.islower()

True

>>> name = 'binges 12'

>>> name.islower()

True

>>> name = 'binges Wang'

>>> name.islower()

False

####

isprintable()

>>> name = 'binges      wang'

>>> name.isprintable()

False

>>> name = 'binges wang'

>>> name.isprintable()

True

>>> name = 'binges\nwang'

>>> name.isprintable()

False

####

isspace()

>>> name = '  '    #两个空格

>>> name.isspace()

True

>>> name = '    '    #一个tab键

>>> name.isspace()

True

>>> name = 'bings wang'

>>> name.isspace()

False

####

istitle()

>>> name = 'binges wang'

>>> name.istitle()

False

>>> name = 'Binges wang'

>>> name.istitle()

False

>>> name = 'Binges Wang'

>>> name.istitle()

True

####

isupper()

>>> name = 'BINGEs'

>>> name.isupper()

False

>>> name = 'BINGES'

>>> name.isupper()

True

>>> name = 'BINGES WANG'

>>> name.isupper()

True

####

join()

>>> a = ' '    #一个空格

>>> a.join(b)

'b i n g e s'

####

ljust()

>>> name = 'binges'

>>> name.ljust(10)

'binges    '

>>> name.ljust(10,'&')

'binges&&&&'

####

lower()

>>> name = 'BinGes WanG'

>>> name.lower()

'binges wang'

>>> name

'BinGes WanG'

####

lstrip()

>>> name = '    binges wang'    #一个空格和一个tab键

>>> name.lstrip()

'binges wang'

####

partition('n')

>>> name = 'binges wang'

>>> name.partition('n')

('bi', 'n', 'ges wang')

####

replace()

>>> name = 'binges wang'

>>> name.replace('n','w')

'biwges wawg'

>>> name

'binges wang'

>>> name.replace('n','w',1)

'biwges wang'

####

startswith()

>>> name = 'binges'

>>> name.startswith('b')

True

>>> name.startswith('bd')

False

>>> name.startswith('n',1,5)

False

>>> name.startswith('n',2,5)

True

####

split()

>>> name = 'binges'

>>> name.split('n')

['bi', 'ges']

>>> name = 'binges wang'

>>> name.split('n')

['bi', 'ges wa', 'g']

>>> name.split('n',1)

['bi', 'ges wang']

####

strip()

>>> name = '    binges  wang    '    #空白处都为一个空格和一个tab键

>>> name.strip()

'binges \twang'

####

swapcase()

>>> name = 'BinGes WanG'

>>> name.swapcase()

'bINgES wANg'

####

title()

>>> name = 'BinGes WanG'

>>> name.title()

'Binges Wang'

####

upper()

>>> name

'BinGes WanG'

>>> name.upper()

'BINGES WANG'

####

zfill(10)

>>> name = 'binges'

>>> name.zfill(10)

'0000binges'

####