str字符串帮助文档

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'.
 
Methods defined here:
__add__(self, value, /)
Return self+value.
__contains__(self, key, /)
Return key in self.
__eq__(self, value, /)
Return self==value.
__format__(...)
S.__format__(format_spec) -> str
 
Return a formatted version of S as described by format_spec.
__ge__(self, value, /)
Return self>=value.
__getattribute__(self, name, /)
Return getattr(self, name).
__getitem__(self, key, /)
Return self[key].
__getnewargs__(...)
__gt__(self, value, /)
Return self>value.
__hash__(self, /)
Return hash(self).
__iter__(self, /)
Implement iter(self).
__le__(self, value, /)
Return self<=value.
__len__(self, /)
Return len(self).
__lt__(self, value, /)
Return self<value.
__mod__(self, value, /)
Return self%value.
__mul__(self, value, /)
Return self*value.n
__ne__(self, value, /)
Return self!=value.
__new__(*args, **kwargs) from builtins.type
Create and return a new object.  See help(type) for accurate signature.
__repr__(self, /)
Return repr(self).
__rmod__(self, value, /)
Return value%self.
__rmul__(self, value, /)          #Return self*value.
__sizeof__(...)                        #S.__sizeof__() -> size of S in memory, in bytes
__str__(self, /)                       #Return str(self).

capitalize(...)                          #S.capitalize() -> str
Return a capitalized version of S, i.e. make the first character
have upper case and the rest lower case. 返回将首字母大写的字符串

casefold(...)
S.casefold() -> str 
Return a version of S suitable for caseless comparisons.

center(...)        #将S用字符fillchar填充扩展到width宽返回该字符串
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)

count(...)        #统计子串‘sub’在S中的个数
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.

encode(...)    #编码字符串为bytes
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.

endswith(...)                # 判断字符串S是否以 suffix 字符结尾，是则返回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.

expandtabs(...)          # 将字符串中‘\t’制表符以tabsize长度的空格代替
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.

find(...)                       # 查找子串sub在S中的第一次出现的位置的下标值
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(...)                  #格式化字符串 ："a = {}，b={}".format(1,2) ，返回'a = 1，b=2'
S.format(*args, **kwargs) -> str
Return a formatted version of S, using substitutions from args and kwargs.
The substitutions are identified by braces ('{' and '}').

format_map(...)
S.format_map(mapping) -> str
Return a formatted version of S, using substitutions from mapping.
The substitutions are identified by braces ('{' and '}').

index(...)            #获取子串第一次出现的下标
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.

isalnum(...)        #字符串由数字组成，返回true，否则返回false
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.

isdecimal(...)   #print u"2".isdecimal()         返回true
S.isdecimal() -> bool
Return True if there are only decimal characters 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.

isidentifier(...)
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".

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.

isnumeric(...)
S.isnumeric() -> bool
Return True if there are only numeric characters in S, False otherwise.

isprintable(...)
S.isprintable() -> bool
Return True if all characters in S are considered printable in repr() or S is empty, 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. upper- and titlecase 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) -> str
Return a string which is the concatenation of the strings in the iterable.  The separator between elements is S.

ljust(...)
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).

lower(...)
S.lower() -> str
Return a copy of the string S converted to lowercase.

lstrip(...)
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.

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]) -> 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.

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
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.

rjust(...)
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).

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=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.

rstrip(...)
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.

split(...)      # s.split(' ',5)，以字符串' '对s进行切片，切成5部分，返回结果为列表
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.

splitlines(...)
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.

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(...)          # 去掉字符串头尾的空格
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.

swapcase(...)
S.swapcase() -> str
Return a copy of S with uppercase characters converted to lowercase
and vice versa.

title(...)          # s.title()   将字符串中每个单词首字母改成大写
S.title() -> str 
Return a titlecased version of S, i.e. words start with title case
characters, all remaining cased characters have lower case.

translate(...)    #
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.

upper(...)
S.upper() -> str
Return a copy of S converted to uppercase.

zfill(...)
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.
Static methods defined here:

maketrans(x, y=None, z=None, /)
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.