DAY14 PYTHON 数据类型 字符串

  变量的作用就是保存状态。

  name='apple'  'apple'才是内存变量，name只是内存变量的引用。

  y=x=a=1

  x,y=1,2 x,y=y,x

  

 这图来自老司机蠢驴

 字符串  它是一个有序的字符的集合，用于存储和表示基本的文本信息， " "  或' '中间包含的内容。

   name='applehalf'

   移除空白   name.strip()

   分割 name.split('|')

   长度 len(name)

    索引  name[3]   name[-1]    python个数从0算起

    切片 name[0:5:2]  

    

s为字符串
s.isalnum() 所有字符都是数字或者字母
s.isalpha() 所有字符都是字母
s.isdigit() 所有字符都是数字
s.islower() 所有字符都是小写
s.isupper() 所有字符都是大写
s.istitle() 所有单词都是首字母大写，像标题
s.isspace() 所有字符都是空白字符、\t、\n、\r

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__        """        首字母变大写        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__        """        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__        """        原来字符居中，不够用空格补全        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__        """         从一个范围内的统计某str出现次数        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__        """        encode(encoding='utf-8',errors='strict')        以encoding指定编码格式编码，如果出错默认报一个ValueError，除非errors指定的是        ignore或replace        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__        """        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__        """        将字符串中包含的\t转换成tabsize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__        """        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(self, *args, **kwargs): # known special case of str.format        """        格式化输出        三种形式：        形式一.        >>> print('{0}{1}{0}'.format('a','b'))        aba        形式二：（必须一一对应）        >>> print('{}{}{}'.format('a','b'))        Traceback (most recent call last):          File "<input>", line 1, in <module>        IndexError: tuple index out of range        >>> print('{}{}'.format('a','b'))        ab        形式三：        >>> print('{name} {age}'.format(age=12,name='lhf'))        lhf 12        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__        """        与format区别        '{name}'.format(**dict(name='alex'))        '{name}'.format_map(dict(name='alex'))        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__        """        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__        """        至少一个字符，且都是字母或数字才返回True        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__        """        至少一个字符，且都是字母才返回True        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__        """        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__        """        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__        """        字符串为关键字返回True        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__        """        至少一个字符，且都是小写字母才返回True        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__        """        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__        """        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__        """        至少一个字符，且都是空格才返回True        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__        """        >>> a='Hello'        >>> a.istitle()        True        >>> a='HellP'        >>> a.istitle()        False        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__        """        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__        """        #对序列进行操作（分别使用' '与':'作为分隔符）        >>> seq1 = ['hello','good','boy','doiido']        >>> print ' '.join(seq1)        hello good boy doiido        >>> print ':'.join(seq1)        hello:good:boy:doiido        #对字符串进行操作        >>> seq2 = "hello good boy doiido"        >>> print ':'.join(seq2)        h:e:l:l:o: :g:o:o:d: :b:o:y: :d:o:i:i:d:o        #对元组进行操作        >>> seq3 = ('hello','good','boy','doiido')        >>> print ':'.join(seq3)        hello:good:boy:doiido        #对字典进行操作        >>> seq4 = {'hello':1,'good':2,'boy':3,'doiido':4}        >>> print ':'.join(seq4)        boy:good:doiido:hello        #合并目录        >>> import os        >>> os.path.join('/hello/','good/boy/','doiido')        '/hello/good/boy/doiido'        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__        """        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__        """        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__        """        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__        """        以sep为分割，将S分成head,sep,tail三部分        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__        """        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 ""    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__        """        以sep为分割，将S切分成列表，与partition的区别在于切分结果不包含sep，        如果一个字符串中包含多个sep那么maxsplit为最多切分成几部分        >>> a='a,b c\nd\te'        >>> a.split()        ['a,b', 'c', 'd', 'e']        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__        """        Python splitlines() 按照行('\r', '\r\n', \n')分隔，        返回一个包含各行作为元素的列表，如果参数 keepends 为 False，不包含换行符，如        果为 True，则保留换行符。        >>> x        'adsfasdf\nsadf\nasdf\nadf'        >>> x.splitlines()        ['adsfasdf', 'sadf', 'asdf', 'adf']        >>> x.splitlines(True)        ['adsfasdf\n', 'sadf\n', 'asdf\n', 'adf']        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__        """        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__        """        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__        """        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__        """        table=str.maketrans('alex','big SB')        a='hello abc'        print(a.translate(table))        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__        """        S.upper() -> str        Return a copy of S converted to uppercase.        """        return ""    def zfill(self, width): # real signature unknown; restored from __doc__        """        原来字符右对齐，不够用0补齐                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 ""    def __add__(self, *args, **kwargs): # real signature unknown        """ Return self+value. """        pass    def __contains__(self, *args, **kwargs): # real signature unknown        """ Return key in self. """        pass    def __eq__(self, *args, **kwargs): # real signature unknown        """ Return self==value. """        pass    def __format__(self, format_spec): # real signature unknown; restored from __doc__        """        S.__format__(format_spec) -> str        Return a formatted version of S as described by format_spec.        """        return ""    def __getattribute__(self, *args, **kwargs): # real signature unknown        """ Return getattr(self, name). """        pass    def __getitem__(self, *args, **kwargs): # real signature unknown        """ Return self[key]. """        pass    def __getnewargs__(self, *args, **kwargs): # real signature unknown        pass    def __ge__(self, *args, **kwargs): # real signature unknown        """ Return self>=value. """        pass    def __gt__(self, *args, **kwargs): # real signature unknown        """ Return self>value. """        pass    def __hash__(self, *args, **kwargs): # real signature unknown        """ Return hash(self). """        pass    def __init__(self, value='', encoding=None, errors='strict'): # known special case of str.__init__        """        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'.        # (copied from class doc)        """        pass    def __iter__(self, *args, **kwargs): # real signature unknown        """ Implement iter(self). """        pass    def __len__(self, *args, **kwargs): # real signature unknown        """ Return len(self). """        pass    def __le__(self, *args, **kwargs): # real signature unknown        """ Return self<=value. """        pass    def __lt__(self, *args, **kwargs): # real signature unknown        """ Return self<value. """        pass    def __mod__(self, *args, **kwargs): # real signature unknown        """ Return self%value. """        pass    def __mul__(self, *args, **kwargs): # real signature unknown        """ Return self*value.n """        pass    @staticmethod # known case of __new__    def __new__(*args, **kwargs): # real signature unknown        """ Create and return a new object.  See help(type) for accurate signature. """        pass    def __ne__(self, *args, **kwargs): # real signature unknown        """ Return self!=value. """        pass    def __repr__(self, *args, **kwargs): # real signature unknown        """ Return repr(self). """        pass    def __rmod__(self, *args, **kwargs): # real signature unknown        """ Return value%self. """        pass    def __rmul__(self, *args, **kwargs): # real signature unknown        """ Return self*value. """        pass    def __sizeof__(self): # real signature unknown; restored from __doc__        """ S.__sizeof__() -> size of S in memory, in bytes """        pass    def __str__(self, *args, **kwargs): # real signature unknown        """ Return str(self). """        pass字符串工厂函数字符串工厂函数

 上边是驴哥总结的str()函数用法