python3.x 基础一：str字符串方法
*字符串不能更改值
数据类型字符串str
- | capitalize(...) 返回字符串中第一个字母大写
| S.capitalize() -> str
|
| Return a capitalized version of S, i.e. make the first character
| have upper case and the rest lower case.
>>> str1='i am chinese' >>> str1.capitalize() 'I am chinese' - | casefold(...) 将大写转换成小写
| S.casefold() -> str
|
| Return a version of S suitable for caseless comparisons.
>>> str2='I AM A CHINESE' >>> str2.casefold() 'i am a chinese' - | center(...) 第一个参数是总字符长度，第二个是补全字符，原字符串居中
| 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)
>>> str1.center(50,'#') '###################i am chinese###################' - | count(...) 计算某个字符/元素出现次数
| 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.
>>> str1.count('e')
2
>>> str1.count('i')
2
>>> str1.count('a')
1 - | endswith(...) 是否以某个后缀字符串结束
| 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.
>>> str2.endswith('SE') True >>> str2.endswith('S') False>>> str = "this is string example....wow!!!"; >>> suffix = "is" >>> print (str.endswith(suffix, 2, 6)) False >>> print(str[2:7]) is is #字符串含有指定后缀，为什么不是返回真？
#理解错误，起始位置是左闭右开
>>> print (str.endswith(suffix, 2,7))
True - | expandtabs(...) 扩展tab字符n个
| 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.
>>> str4='I am \t Chinese' >>> str4.expandtabs(10) 'I am Chinese' - | find(...) 返回查找到的第一个字符位置，否则返回-1
| 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.
>>> str2 'I AM A CHINESE' >>> str2.find('M') 3 >>> str2.find('A') 2 >>> str2.find('B') -1 - | index(...) 同上，查找不到则报错
| S.index(sub[, start[, end]]) -> int
|
| Like S.find() but raise ValueError when the substring is not found.
>>> str2 'I AM A CHINESE' >>> str2.index('A') 2 >>> str2.index('B') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: substring not found - | isalnum(...) 判断字符串是否由字母数字组成
| S.isalnum() -> bool
|
| Return True if all characters in S are alphanumeric
| and there is at least one character in S, False otherwise.
>>> str5='I am 1 chinese' >>> str5.isalnum() False >>> str6='iAm1Chinese' >>> str6.isalnum() True - | isalpha(...) 判断字符串是否全部是字符组成
| S.isalpha() -> bool
|
| Return True if all characters in S are alphabetic
| and there is at least one character in S, False otherwise.
>>> str7='iamChinese' >>> str7.isalpha() True >>> str3.isalpha() False - | isdecimal(...) 如果字符串是否只包含十进制字符返回True，否则返回False
| S.isdecimal() -> bool
|
| Return True if there are only decimal characters in S,
| False otherwise.
>>> str8=u'asdfasdf1000' >>> str8.isdecimal() False >>> stru=u'1000' >>> stru.isdecimal() True - | isdigit(...) 判断字符串中是否全部是数字
| S.isdigit() -> bool
|
| Return True if all characters in S are digits
| and there is at least one character in S, False otherwise.
>>> str9,str10='abc123','123' >>> str9.isdigit() False >>> str10.isdigit() True - | isidentifier(...) 判断变量明明是否合法
| 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(...) 判断字符串中所有字母是否小写
| 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.
>>> str11,str12,str13='abcd','AbCd','Ab123' >>> str11.islower() True >>> str12.islower() False >>> str13.islower() False >>> str14='aa123' >>> str14.islower() True - | isnumeric(...) 判断字符串中所有字符是否是数字
| S.isnumeric() -> bool
|
| Return True if there are only numeric characters in S,
| False otherwise.
>>> str10,str14 ('123', 'aa123') >>> str10.isnumeric() True >>> str14.isnumeric() False - | isspace(...) 判断字符是否是空格
| S.isspace() -> bool
|
| Return True if all characters in S are whitespace
| and there is at least one character in S, False otherwise.
>>> str1,str14,str15
('i am chinese', 'aa123', ' ')
>>> str1.isspace(),str14.isspace(),str15.isspace()
(False, False, True) - | istitle(...) 判断字符串是否是标题，标题单词首字母均大写
| 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.
>>> str16,str17='I Am Chinese','I am chinese' >>> str16.istitle(),str17.istitle() (True, False) - | isupper(...) 判断字符串中字母是否全部是大写
| 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.
>>> str18,str19='ABC123','Abc123' >>> str18.isupper(),str19.isupper() (True, False) - | join(...) 将其他可迭代对象转换成字符串，S表示字符串分隔符
| S.join(iterable) -> str
|
| Return a string which is the concatenation of the strings in the
| iterable. The separator between elements is S.
>>> list1=['a','b','c','d']
>>> ','.join(list1)
'a,b,c,d'
>>> ''.join(list1)
'abcd'
>>> ' '.join(list1)
'a b c d' - | ljust(...) 共width个位置，字符串靠左，右边以字符填充
| 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).
>>> str10 '123' >>> str10.ljust(10,'#') '123#######' - | lower(...) 将字符串中所有大写字母转换成小写
| S.lower() -> str
|
| Return a copy of the string S converted to lowercase.
View Code - | lstrip(...) 将左边空格剪掉，可以指定其他被剪掉空格，\n \t
| 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.
>>> str20=' 123abc ABC ' >>> str20.lstrip() '123abc ABC 'strip()将左右两边空格剪掉，rstrip()将右边空格剪掉
- | partition(...) 以某个字符切片字符串，返回三元组，中间是分隔符，找不到则返回源字符串和2个空格
| 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.
>>> str21='http://www.baidu.com' >>> str21.partition('://'... ) ('http', '://', 'www.baidu.com') >>> str21.partition('abc') ('http://www.baidu.com', '', '') - | replace(...) 字符替换，默认全部替换，如指定计数则替换指定计数个数字符
| 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.
>>> str21 'http://www.baidu.com' >>> str21.replace('baidu','jd') 'http://www.jd.com' >>> str21.replace('w','z') 'http://zzz.baidu.com' >>> str21.replace('w','z',1) 'http://zww.baidu.com' - | rfind(...) 从左往右查找，并返回最右边的字符索引位置
| 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.
>>> str21 'http://www.baidu.com' >>> str21.rfind('b') 11 >>> str21.rfind('w') 9 - | rindex(...)
| S.rindex(sub[, start[, end]]) -> int
|
| Like S.rfind() but raise ValueError when the substring is not found. - | rjust(...) 字符靠右，左边补全字符，默认空格
| 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).
| 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).>>> str10.rjust(10,'x') 'xxxxxxx123' - | rpartition(...) 无法找到切片字符串，则源字符串索引是2，前面是空格
| 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.
>>> str21.rpartition('://') ('http', '://', 'www.baidu.com') >>> str21.rpartition('abc') ('', '', 'http://www.baidu.com') - | split(...) 默认分隔符空格 \t \n，可以指定分割次数
| 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.
>>> str21.split('w') ['http://', '', '', '.baidu.com'] >>> str21.split('w',1) ['http://', 'ww.baidu.com'] >>> str21.split('w',2) ['http://', '', 'w.baidu.com'] >>> str21.split('w',3) ['http://', '', '', '.baidu.com'] - | rsplit(...) 右边第一个分割符开始切分，默认全切分，可以指定分割次数
| 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.
>>> str21.rsplit('w') ['http://', '', '', '.baidu.com'] >>> str21.rsplit('w',1) ['http://ww', '.baidu.com'] >>> str21.rsplit('w',2) ['http://w', '', '.baidu.com'] >>> str21.rsplit('w',3) ['http://', '', '', '.baidu.com'] - | splitlines(...) 行分割
| 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.
>>> str22='www\nbaidu\ncom' >>> str22.splitlines() ['www', 'baidu', 'com'] - | startswith(...) 同endswith()
| 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. - | swapcase(...) 字符串中大小写转换，大写变小写，小写变大写--- upper()，lower()
| S.swapcase() -> str
|
| Return a copy of S with uppercase characters converted to lowercase
| and vice versa.
>>> str23='asdf123' >>> str23.swapcase() 'ASDF123' >>> str24='ABcd222' >>> str24.swapcase() 'abCD222' - | title(...) 返回一个titile标题
| S.title() -> str
|
| Return a titlecased version of S, i.e. words start with title case
| characters, all remaining cased characters have lower case.
>>> str25='a good persion asdf 213' >>> str25.title() 'A Good Persion Asdf 213' - | zfill(...) 总长width个字符，前面补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.
>>> str25.zfill(30)
'0000000a good persion asdf 213'
