python str 类

红太狼 2022-05-21 05:51 189阅读 0赞

# 类功能介绍 #

python 中字符串等价于str类。  
**判断方法**  
isalnum(self):is alphanumerical，全是字母数字组合且至少有一个字符  
isalpha(self):is alphaberic，全是字母数且至少有一个字符  
isdecimal(self):= is decimal ，仅十进制数字  
isdigit(self):= is digit ，仅数字  
isidentifier(self):= is identier ，是有效变量名，保留字使用keyword.iskeyword()  
islower(self): = is lower 全是小写字母且至少有一个小写字符  
isnumeric(self):=is numeric，是数字  
isprintable(self):=is printable，没有空字符  
isspace(self):= is whitespace。最少有一个空格  
istitle(self):=is titlecased 是标题  
isupper(self):=is supper 全是大写字母且至少有一个大写字符  
**操作方法**

encode(self, encoding=‘utf-8’, errors=‘strict’):编码，默认utf-8  
center(self, width, fillchar=None): 两边添加fillchar字符，总长度为width，默认空格  
join(self, iterable): iterable（可迭代的）的每一个对下中插入字符串

lower(self):变小写  
upper(self):便大写  
swapcase(self): 转换大小写  
casefold:素有大写变成小写（非英语语言字母也可以）  
capitalize: 时第一个字母变成大写  
count(self, sub, start=None, end=None): 从start 到end 之间非重子字符串sub的次数  
expandtabs: 字符串中的 tab 符号(’\\t’)转为空格，tab 符号(’\\t’)默认的空格数是 8。

ljust(self, width, fillchar=None): left-justified（左对齐）使用fillchar填充，总长度width 默认使用空格  
rjust(self, width, fillchar=None): right-justified 右对齐，同上  
zfill(self, width):同rjust以9填充的的结果zero fill

lstrip(self, chars=None): 删除字符串右边的char字符。默认空格  
rstrip(self, chars=None): 删除字符串左边的char字符，默认空格  
strip(self, chars=None):删除字符串两边的的char字符，默认空格

maketrans(self, \*args, \*\*kwargs): make translation table 用于str.translate()，参数一为需要转换的字符组成的字符串。参数二为转换的目标字符组成的字符串。，参数三为可选参数，表示要删除的字符组成的字符串。，一和而参数必须长度一样  
translate(self, table): table 为str.translate 返回的表

partition(self, sep): 一sep 分割字符串，翻译各异三元数组，中间为分隔符  
rpartition(self, sep): partion方向相反

split(self, sep=None, maxsplit=-1)从左向右寻找sep，然后除去sep字符分割成两部分放入列表中，maxsplit为最大次数  
rsplit(self, sep=None, maxsplit=-1):从右向左寻找sep，同上  
splitlines(self, keepends=None):按换行符分割，默认不保留换行符，除非keepends为True

replace(self, old, new, count=None):把old 字符串替换成new 字符串，count 为只能替换的次数  
title(self): 单词首字母大写

endswith(self, suffix, start=None, end=None):start 到end 之间以suffix结尾  
startswith(self, prefix, start=None, end=None):同上

find(self, sub, start=None, end=None):从start 到end 之间，子字符串sub 最小索引，找不到返回-1  
rfind(self, sub, start=None, end=None):从start 到end 之间，子字符串sub 最小索引，找不到返回-1

index(self, sub, start=None, end=None): 和find一样,不过找不到 抛出ValueError  
rindex(self, sub, start=None, end=None):和rfind一样,不过找不到 抛出ValueError

format(self, \*args, \*\*kwargs):格式化字符串  
format\_map(self, mapping): 用一个字典对象错参数格式化

\#语法介绍\#  
因为字符串是数组，所以我们可以使用\[\]符号操作，词操作叫做"切片"

**语法：** str\[start: end :step\]，start开始位置，end 结束位置，step 步长，选取start 到end-1之间步长为1的字符

• \[:\] 提取从开头（默认位置0）到结尾（默认位置-1）的整个字符串  
• \[start:\] 从start 提取到结尾  
• \[:end\] 从开头提取到end - 1  
• \[start:end\] 从start 提取到end - 1  
• \[start: end: step\] 从start 提取到end - 1，每step 个字符提取一个  
•\[-3:\] 倒数第三个到结尾  
• \[::5\] 开始到第4个  
• \[::-1\]反转（reverse）字符串

# 附录 #

python3.6 str类（看英语的真累╮(╯▽╰)╭）

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__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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
            """ 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__
            """ S.index(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. Raises ValueError when the substring is not found. """
            return 0
    
        def isalnum(self): # real signature unknown; restored from __doc__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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 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. Raises 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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__
            """ 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