基本数据类型
二、字符串
字符串(String)是由零个或多个字符组成的有限序列，在编程语言中表示文本。
1.字符串格式
Python用一对引号来生成字符串，单引号或者双引号都可以：
"hello,world"'hello,world'
2.字符串的运算
字符串支持两种运算：加法和数乘。
加法操作是将两个字符串按照顺序相连，如：
v = "hello" + "world"print(v) #结果为:helloworld
数乘是将字符串与一个整数相乘，得到重复的字符串：
v = "abc" * 3print(v) #结果为:abcabcabc
3.字符串的方法
字符串一些常用的方法。
（1）.find()方法
.find()方法是查找元素，将字符串从开始往后找，找到第一个之后，获取其位置，未找到结果为-1，可以设定起始位置和结束位置。
test="alexalex"v=test.find('ex',5,8) #查找ex 从5开始找,结束位置8print(v) #结果为:6 （2）.join()方法
.join()方法的作用是将字符串中的每一个元素按照指定分隔符进行拼接。
test="abc"t="_"v=t.join(test) #也可以直接使用v="_".join(test)print(v) #结果为:a_b_c
（3）.lower()方法
.lower()方法将字符串字母转换为小写
test="abcDeF"v = test.lower()print(v) #结果为:abcdef
（4）.upper方法
.upper方法将字符串字母转换为大写
test="abcDeF"v = test.upper()print(v) #结果为:ABCDEF
（5）.strip()方法
.strip()方法是将去除两端多余的空格、还可以去除\t 、\n，还可以去除指定内容。
test="aasabcsda"v = test.strip("a")print(v) #结果为:sabcsd .lstrip()方法是去除开头多余的空格
.rstrip()方法是去除结尾多余的空格
（6）.split()方法
.split()方法将字符串分割，并返回一个字符串列表。可指定分隔符以及次数。
test="1,2,3,4,5"v = test.split(",",2) # 以","为分隔符，分割两次print(v) #结果为:['1', '2', '3,4,5'] （7）.replace()方法
.replace()方法将字符串中的指定部分替换成新的内容。
test="hello world"v = test.replace("world","python")print(v) #结果为:hello python （8）.format()方法
.format()方法将字符串进行格式化，将一个字符串中的占位符替换为指定的值
test = 'i am {name}，age {a}'v = test.format(name='alex',a=19)print(v) #结果为i am alex,age 19 字符串所有方法归纳：
1 class str(basestring): 2 """ 3 str(object='') -> string 4 5 Return a nice string representation of the object. 6 If the argument is a string, the return value is the same object. 7 """ 8 def capitalize(self): 9 """ 首字母变大写 """ 10 """ 11 S.capitalize() -> string 12 13 Return a copy of the string S with only its first character 14 capitalized. 15 """ 16 return "" 17 18 def center(self, width, fillchar=None): 19 """ 内容居中，width：总长度；fillchar：空白处填充内容，默认无 """ 20 """ 21 S.center(width[, fillchar]) -> string 22 23 Return S centered in a string of length width. Padding is 24 done using the specified fill character (default is a space) 25 """ 26 return "" 27 28 def count(self, sub, start=None, end=None): 29 """ 子序列个数 """ 30 """ 31 S.count(sub[, start[, end]]) -> int 32 33 Return the number of non-overlapping occurrences of substring sub in 34 string S[start:end]. Optional arguments start and end are interpreted 35 as in slice notation. 36 """ 37 return 0 38 39 def decode(self, encoding=None, errors=None): 40 """ 解码 """ 41 """ 42 S.decode([encoding[,errors]]) -> object 43 44 Decodes S using the codec registered for encoding. encoding defaults 45 to the default encoding. errors may be given to set a different error 46 handling scheme. Default is 'strict' meaning that encoding errors raise 47 a UnicodeDecodeError. Other possible values are 'ignore' and 'replace' 48 as well as any other name registered with codecs.register_error that is 49 able to handle UnicodeDecodeErrors. 50 """ 51 return object() 52 53 def encode(self, encoding=None, errors=None): 54 """ 编码，针对unicode """ 55 """ 56 S.encode([encoding[,errors]]) -> object 57 58 Encodes S using the codec registered for encoding. encoding defaults 59 to the default encoding. errors may be given to set a different error 60 handling scheme. Default is 'strict' meaning that encoding errors raise 61 a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and 62 'xmlcharrefreplace' as well as any other name registered with 63 codecs.register_error that is able to handle UnicodeEncodeErrors. 64 """ 65 return object() 66 67 def endswith(self, suffix, start=None, end=None): 68 """ 是否以 xxx 结束 """ 69 """ 70 S.endswith(suffix[, start[, end]]) -> bool 71 72 Return True if S ends with the specified suffix, False otherwise. 73 With optional start, test S beginning at that position. 74 With optional end, stop comparing S at that position. 75 suffix can also be a tuple of strings to try. 76 """ 77 return False 78 79 def expandtabs(self, tabsize=None): 80 """ 将tab转换成空格，默认一个tab转换成8个空格 """ 81 """ 82 S.expandtabs([tabsize]) -> string 83 84 Return a copy of S where all tab characters are expanded using spaces. 85 If tabsize is not given, a tab size of 8 characters is assumed. 86 """ 87 return "" 88 89 def find(self, sub, start=None, end=None): 90 """ 寻找子序列位置，如果没找到，返回 -1 """ 91 """ 92 S.find(sub [,start [,end]]) -> int 93 94 Return the lowest index in S where substring sub is found, 95 such that sub is contained within S[start:end]. Optional 96 arguments start and end are interpreted as in slice notation. 97 98 Return -1 on failure. 99 """100 return 0101 102 def format(*args, **kwargs): # known special case of str.format103 """ 字符串格式化，动态参数，将函数式编程时细说 """104 """105 S.format(*args, **kwargs) -> string106 107 Return a formatted version of S, using substitutions from args and kwargs.108 The substitutions are identified by braces ('{' and '}').109 """110 pass111 112 def index(self, sub, start=None, end=None): 113 """ 子序列位置，如果没找到，报错 """114 S.index(sub [,start [,end]]) -> int115 116 Like S.find() but raise ValueError when the substring is not found.117 """118 return 0119 120 def isalnum(self): 121 """ 是否是字母和数字 """122 """123 S.isalnum() -> bool124 125 Return True if all characters in S are alphanumeric126 and there is at least one character in S, False otherwise.127 """128 return False129 130 def isalpha(self): 131 """ 是否是字母 """132 """133 S.isalpha() -> bool134 135 Return True if all characters in S are alphabetic136 and there is at least one character in S, False otherwise.137 """138 return False139 140 def isdigit(self): 141 """ 是否是数字 """142 """143 S.isdigit() -> bool144 145 Return True if all characters in S are digits146 and there is at least one character in S, False otherwise.147 """148 return False149 150 def islower(self): 151 """ 是否小写 """152 """153 S.islower() -> bool154 155 Return True if all cased characters in S are lowercase and there is156 at least one cased character in S, False otherwise.157 """158 return False159 160 def isspace(self): 161 """162 S.isspace() -> bool163 164 Return True if all characters in S are whitespace165 and there is at least one character in S, False otherwise.166 """167 return False168 169 def istitle(self): 170 """171 S.istitle() -> bool172 173 Return True if S is a titlecased string and there is at least one174 character in S, i.e. uppercase characters may only follow uncased175 characters and lowercase characters only cased ones. Return False176 otherwise.177 """178 return False179 180 def isupper(self): 181 """182 S.isupper() -> bool183 184 Return True if all cased characters in S are uppercase and there is185 at least one cased character in S, False otherwise.186 """187 return False188 189 def join(self, iterable): 190 """ 连接 """191 """192 S.join(iterable) -> string193 194 Return a string which is the concatenation of the strings in the195 iterable. The separator between elements is S.196 """197 return ""198 199 def ljust(self, width, fillchar=None): 200 """ 内容左对齐，右侧填充 """201 """202 S.ljust(width[, fillchar]) -> string203 204 Return S left-justified in a string of length width. Padding is205 done using the specified fill character (default is a space).206 """207 return ""208 209 def lower(self): 210 """ 变小写 """211 """212 S.lower() -> string213 214 Return a copy of the string S converted to lowercase.215 """216 return ""217 218 def lstrip(self, chars=None): 219 """ 移除左侧空白 """220 """221 S.lstrip([chars]) -> string or unicode222 223 Return a copy of the string S with leading whitespace removed.224 If chars is given and not None, remove characters in chars instead.225 If chars is unicode, S will be converted to unicode before stripping226 """227 return ""228 229 def partition(self, sep): 230 """ 分割，前，中，后三部分 """231 """232 S.partition(sep) -> (head, sep, tail)233 234 Search for the separator sep in S, and return the part before it,235 the separator itself, and the part after it. If the separator is not236 found, return S and two empty strings.237 """238 pass239 240 def replace(self, old, new, count=None): 241 """ 替换 """242 """243 S.replace(old, new[, count]) -> string244 245 Return a copy of string S with all occurrences of substring246 old replaced by new. If the optional argument count is247 given, only the first count occurrences are replaced.248 """249 return ""250 251 def rfind(self, sub, start=None, end=None): 252 """253 S.rfind(sub [,start [,end]]) -> int254 255 Return the highest index in S where substring sub is found,256 such that sub is contained within S[start:end]. Optional257 arguments start and end are interpreted as in slice notation.258 259 Return -1 on failure.260 """261 return 0262 263 def rindex(self, sub, start=None, end=None): 264 """265 S.rindex(sub [,start [,end]]) -> int266 267 Like S.rfind() but raise ValueError when the substring is not found.268 """269 return 0270 271 def rjust(self, width, fillchar=None): 272 """273 S.rjust(width[, fillchar]) -> string274 275 Return S right-justified in a string of length width. Padding is276 done using the specified fill character (default is a space)277 """278 return ""279 280 def rpartition(self, sep): 281 """282 S.rpartition(sep) -> (head, sep, tail)283 284 Search for the separator sep in S, starting at the end of S, and return285 the part before it, the separator itself, and the part after it. If the286 separator is not found, return two empty strings and S.287 """288 pass289 290 def rsplit(self, sep=None, maxsplit=None): 291 """292 S.rsplit([sep [,maxsplit]]) -> list of strings293 294 Return a list of the words in the string S, using sep as the295 delimiter string, starting at the end of the string and working296 to the front. If maxsplit is given, at most maxsplit splits are297 done. If sep is not specified or is None, any whitespace string298 is a separator.299 """300 return []301 302 def rstrip(self, chars=None): 303 """304 S.rstrip([chars]) -> string or unicode305 306 Return a copy of the string S with trailing whitespace removed.307 If chars is given and not None, remove characters in chars instead.308 If chars is unicode, S will be converted to unicode before stripping309 """310 return ""311 312 def split(self, sep=None, maxsplit=None): 313 """ 分割， maxsplit最多分割几次 """314 """315 S.split([sep [,maxsplit]]) -> list of strings316 317 Return a list of the words in the string S, using sep as the318 delimiter string. If maxsplit is given, at most maxsplit319 splits are done. If sep is not specified or is None, any320 whitespace string is a separator and empty strings are removed321 from the result.322 """323 return []324 325 def splitlines(self, keepends=False): 326 """ 根据换行分割 """327 """328 S.splitlines(keepends=False) -> list of strings329 330 Return a list of the lines in S, breaking at line boundaries.331 Line breaks are not included in the resulting list unless keepends332 is given and true.333 """334 return []335 336 def startswith(self, prefix, start=None, end=None): 337 """ 是否起始 """338 """339 S.startswith(prefix[, start[, end]]) -> bool340 341 Return True if S starts with the specified prefix, False otherwise.342 With optional start, test S beginning at that position.343 With optional end, stop comparing S at that position.344 prefix can also be a tuple of strings to try.345 """346 return False347 348 def strip(self, chars=None): 349 """ 移除两段空白 """350 """351 S.strip([chars]) -> string or unicode352 353 Return a copy of the string S with leading and trailing354 whitespace removed.355 If chars is given and not None, remove characters in chars instead.356 If chars is unicode, S will be converted to unicode before stripping357 """358 return ""359 360 def swapcase(self): 361 """ 大写变小写，小写变大写 """362 """363 S.swapcase() -> string364 365 Return a copy of the string S with uppercase characters366 converted to lowercase and vice versa.367 """368 return ""369 370 def title(self): 371 """372 S.title() -> string373 374 Return a titlecased version of S, i.e. words start with uppercase375 characters, all remaining cased characters have lowercase.376 """377 return ""378 379 def translate(self, table, deletechars=None): 380 """381 转换，需要先做一个对应表，最后一个表示删除字符集合382 intab = "aeiou"383 outtab = "12345"384 trantab = maketrans(intab, outtab)385 str = "this is string example....wow!!!"386 print str.translate(trantab, 'xm')387 """388 389 """390 S.translate(table [,deletechars]) -> string391 392 Return a copy of the string S, where all characters occurring393 in the optional argument deletechars are removed, and the394 remaining characters have been mapped through the given395 translation table, which must be a string of length 256 or None.396 If the table argument is None, no translation is applied and397 the operation simply removes the characters in deletechars.398 """399 return ""400 401 def upper(self): 402 """403 S.upper() -> string404 405 Return a copy of the string S converted to uppercase.406 """407 return ""408 409 def zfill(self, width): 410 """方法返回指定长度的字符串，原字符串右对齐，前面填充0。"""411 """412 S.zfill(width) -> string413 414 Pad a numeric string S with zeros on the left, to fill a field415 of the specified width. The string S is never truncated.416 """417 return ""418 419 def _formatter_field_name_split(self, *args, **kwargs): # real signature unknown420 pass421 422 def _formatter_parser(self, *args, **kwargs): # real signature unknown423 pass424 425 def __add__(self, y): 426 """ x.__add__(y) <==> x+y """427 pass428 429 def __contains__(self, y): 430 """ x.__contains__(y) <==> y in x """431 pass432 433 def __eq__(self, y): 434 """ x.__eq__(y) <==> x==y """435 pass436 437 def __format__(self, format_spec): 438 """439 S.__format__(format_spec) -> string440 441 Return a formatted version of S as described by format_spec.442 """443 return ""444 445 def __getattribute__(self, name): 446 """ x.__getattribute__('name') <==> x.name """447 pass448 449 def __getitem__(self, y): 450 """ x.__getitem__(y) <==> x[y] """451 pass452 453 def __getnewargs__(self, *args, **kwargs): # real signature unknown454 pass455 456 def __getslice__(self, i, j): 457 """458 x.__getslice__(i, j) <==> x[i:j]459 460 Use of negative indices is not supported.461 """462 pass463 464 def __ge__(self, y): 465 """ x.__ge__(y) <==> x>=y """466 pass467 468 def __gt__(self, y): 469 """ x.__gt__(y) <==> x>y """470 pass471 472 def __hash__(self): 473 """ x.__hash__() <==> hash(x) """474 pass475 476 def __init__(self, string=''): # known special case of str.__init__477 """478 str(object='') -> string479 480 Return a nice string representation of the object.481 If the argument is a string, the return value is the same object.482 # (copied from class doc)483 """484 pass485 486 def __len__(self): 487 """ x.__len__() <==> len(x) """488 pass489 490 def __le__(self, y): 491 """ x.__le__(y) <==> x<=y """492 pass493 494 def __lt__(self, y): 495 """ x.__lt__(y) <==> x x%y """500 pass501 502 def __mul__(self, n): 503 """ x.__mul__(n) <==> x*n """504 pass505 506 @staticmethod # known case of __new__507 def __new__(S, *more): 508 """ T.__new__(S, ...) -> a new object with type S, a subtype of T """509 pass510 511 def __ne__(self, y): 512 """ x.__ne__(y) <==> x!=y """513 pass514 515 def __repr__(self): 516 """ x.__repr__() <==> repr(x) """517 pass518 519 def __rmod__(self, y): 520 """ x.__rmod__(y) <==> y%x """521 pass522 523 def __rmul__(self, n): 524 """ x.__rmul__(n) <==> n*x """525 pass526 527 def __sizeof__(self): 528 """ S.__sizeof__() -> size of S in memory, in bytes """529 pass530 531 def __str__(self): 532 """ x.__str__() <==> str(x) """533 pass534 535 str 4.转义字符
转义字符是一种表示字符的机制，如换行符“\n”或制表符“\t”。