字符串

定義：它是一個有序的字符的集合，用于存儲和表示基本的文本信息，‘’或“”或‘’‘ ’‘’中間包含的內容稱之為字符串
特性：
1.只能存放一個值
2.不可變，只能重新賦值
3.按照從左到右的順序定義字符集合，下標從0開始順序訪問，有序

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字符串常用功能

移除空白

分割

長度

索引

切片

格式化輸出

詳細舉例，上篇博文有寫

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字符常用內建函數

1 def capitalize(self): # real signature unknown; restored from __doc__ 2 """ 3 B.capitalize() -> copy of B 4 把字符串的第一個字符大寫 5 Return a copy of B with only its first character capitalized (ASCII) 6 and the rest lower-cased. 7 """ 8 pass 9 10 def center(self, width, fillchar=None): # real signature unknown; restored from __doc__ 11 """ 12 B.center(width[, fillchar]) -> copy of B 13 返回一個原字符串居中，并使用空格填充至長度width的新字符 14 Return B centered in a string of length width. Padding is 15 done using the specified fill character (default is a space). 16 """ 17 pass 18 19 def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ 20 """ 21 B.count(sub[, start[, end]]) -> int 22 返回str在string里面出現的次數，如果start或者end指定則返回指定范圍內str出現的次數 23 Return the number of non-overlapping occurrences of subsection sub in 24 bytes B[start:end]. Optional arguments start and end are interpreted 25 as in slice notation. 26 """ 27 return 0 28 29 def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__ 30 """ 31 S.encode(encoding='utf-8', errors='strict') -> bytes 32 以encoding 指定的編碼格式解碼string，如果出錯默認報一個ValueError的異常，除非errors指定的是‘ignore’或者replace 33 Encode S using the codec registered for encoding. Default encoding 34 is 'utf-8'. errors may be given to set a different error 35 handling scheme. Default is 'strict' meaning that encoding errors raise 36 a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and 37 'xmlcharrefreplace' as well as any other name registered with 38 codecs.register_error that can handle UnicodeEncodeErrors. 39 """ 40 pass 41 42 def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__ 43 """ 44 B.endswith(suffix[, start[, end]]) -> bool 45 檢查字符串是否以suffix結束，如果start或者end指定則檢查指定的范圍內是否以suffix結束，如果是返回True，否則返回False 46 Return True if B ends with the specified suffix, False otherwise. 47 With optional start, test B beginning at that position. 48 With optional end, stop comparing B at that position. 49 suffix can also be a tuple of bytes to try. 50 """ 51 return False 52 53 def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__ 54 """ 55 B.expandtabs(tabsize=8) -> copy of B 56 把字符串string中的tab符號\t轉換為空格，默認的空格數tabsize是8 57 Return a copy of B where all tab characters are expanded using spaces. 58 If tabsize is not given, a tab size of 8 characters is assumed. 59 """ 60 pass 61 62 def insert(self, *args, **kwargs): # real signature unknown 63 """ 64 Insert a single item into the bytearray before the given index. 65 66 index 67 The index where the value is to be inserted. 68 item 69 The item to be inserted. 70 """ 71 pass 72 73 def isalnum(self): # real signature unknown; restored from __doc__ 74 """ 75 B.isalnum() -> bool 76 如果string至少有一個字符并且所有字符都是字母或數字則返回True,否則返回False 77 Return True if all characters in B are alphanumeric 78 and there is at least one character in B, False otherwise. 79 """ 80 return False 81 82 def isalpha(self): # real signature unknown; restored from __doc__ 83 """ 84 B.isalpha() -> bool 85 如果string至少有一個字符并且所有字符都是字母則返回True，否則返回False 86 Return True if all characters in B are alphabetic 87 and there is at least one character in B, False otherwise. 88 """ 89 return False 90 91 def isdigit(self): # real signature unknown; restored from __doc__ 92 """ 93 B.isdigit() -> bool 94 如果string只包含十進制數字則返回True，否則返回False 95 Return True if all characters in B are digits 96 and there is at least one character in B, False otherwise. 97 """ 98 return False 99 100 def islower(self): # real signature unknown; restored from __doc__ 101 """ 102 B.islower() -> bool 103 如果string中包含至少一個區分大小寫的字符，并且所有這些（區分大小寫的）字符都是小寫，則返回True，否則返回False 104 Return True if all cased characters in B are lowercase and there is 105 at least one cased character in B, False otherwise. 106 """ 107 return False 108 109 def isspace(self): # real signature unknown; restored from __doc__ 110 """ 111 B.isspace() -> bool 112 如果string中只包含空格，則返回Ture，否則返回False 113 Return True if all characters in B are whitespace 114 and there is at least one character in B, False otherwise. 115 """ 116 return False 117 118 def istitle(self): # real signature unknown; restored from __doc__ 119 """ 120 B.istitle() -> bool 121 如果string是標題化的（就是首字母大寫）則返回True，否則返回False 122 Return True if B is a titlecased string and there is at least one 123 character in B, i.e. uppercase characters may only follow uncased 124 characters and lowercase characters only cased ones. Return False 125 otherwise. 126 """ 127 return False 128 129 def isupper(self): # real signature unknown; restored from __doc__ 130 """ 131 B.isupper() -> bool 132 如果string中包含至少一個區分大小寫的字符，并且所有這些（區分大小寫的）字符都是大寫，則返回True，否則返回False 133 Return True if all cased characters in B are uppercase and there is 134 at least one cased character in B, False otherwise. 135 """ 136 return False 137 138 def join(self, *args, **kwargs): # real signature unknown 139 """ 140 Concatenate any number of bytes/bytearray objects. 141 以string 作為分隔符，將序列中所有的元素(的字符串表示)合并為一個新的字符串 142 The bytearray whose method is called is inserted in between each pair. 143 144 The result is returned as a new bytearray object. 145 """ 146 pass 147 148 def ljust(self, width, fillchar=None): # real signature unknown; restored from __doc__ 149 """ 150 B.ljust(width[, fillchar]) -> copy of B 151 返回一個原字符左對齊，并使用空格填充至長度width的新字符串 152 Return B left justified in a string of length width. Padding is 153 done using the specified fill character (default is a space). 154 """ 155 pass 156 157 def lower(self): # real signature unknown; restored from __doc__ 158 """ 159 B.lower() -> copy of B 160 轉換sting中所有大寫字符為小寫 161 Return a copy of B with all ASCII characters converted to lowercase. 162 """ 163 pass 164 165 def maketrans(*args, **kwargs): # real signature unknown 166 """ 167 Return a translation table useable for the bytes or bytearray translate method. 168 169 The returned table will be one where each byte in frm is mapped to the byte at 170 the same position in to. 171 172 The bytes objects frm and to must be of the same length. 173 """ 174 pass 175 176 def partition(self, sep): # real signature unknown; restored from __doc__ 177 """ 178 S.partition(sep) -> (head, sep, tail) 179 有點像find()和split()的結合體，從str出現的第一個位置起，把字符串string分成一個三字符的元組(string_pre_str,str, 180 string_post_str)，如果string中不包含str則string_pre_str == string. 181 Search for the separator sep in S, and return the part before it, 182 the separator itself, and the part after it. If the separator is not 183 found, return S and two empty strings. 184 """ 185 pass 186 187 def pop(self, *args, **kwargs): # real signature unknown 188 """ 189 Remove and return a single item from B. 190 191 index 192 The index from where to remove the item. 193 -1 (the default value) means remove the last item. 194 195 If no index argument is given, will pop the last item. 196 """ 197 pass 198 199 def remove(self, *args, **kwargs): # real signature unknown 200 """ 201 Remove the first occurrence of a value in the bytearray. 202 203 value 204 The value to remove. 205 """ 206 pass 207 208 def replace(self, old, new, count=None): # real signature unknown; restored from __doc__ 209 """ 210 S.replace(old, new[, count]) -> str 211 把string中的old替換成new，如果count指定，則替換不超過count次 212 Return a copy of S with all occurrences of substring 213 old replaced by new. If the optional argument count is 214 given, only the first count occurrences are replaced. 215 """ 216 return "" 217 def reverse(self, *args, **kwargs): # real signature unknown 218 """ Reverse the order of the values in B in place. """ 219 pass 220 221 def find(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ 222 """ 223 B.find(sub[, start[, end]]) -> int 224 檢測str是否包含在string中，如果start和end指定范圍，則檢查是否包含在指定范圍內，如果是返回開始的索引值，否則返回-1 225 Return the lowest index in B where subsection sub is found, 226 such that sub is contained within B[start,end]. Optional 227 arguments start and end are interpreted as in slice notation. 228 229 Return -1 on failure. 230 """ 231 return 0 232 233 def rfind(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ 234 """ 235 B.rfind(sub[, start[, end]]) -> int 236 類似于find()函數，不過是從右邊開始查找 237 Return the highest index in B where subsection sub is found, 238 such that sub is contained within B[start,end]. Optional 239 arguments start and end are interpreted as in slice notation. 240 241 Return -1 on failure. 242 """ 243 return 0 244 245 def index(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ 246 """ 247 B.index(sub[, start[, end]]) -> int 248 跟find()方法一樣，只不過如果str不在string中會報一個異常 249 Like B.find() but raise ValueError when the subsection is not found. 250 """ 251 return 0 252 253 def rindex(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ 254 """ 255 B.rindex(sub[, start[, end]]) -> int 256 類似于index(),不過是從右邊開始 257 Like B.rfind() but raise ValueError when the subsection is not found. 258 """ 259 return 0 260 261 def rjust(self, width, fillchar=None): # real signature unknown; restored from __doc__ 262 """ 263 B.rjust(width[, fillchar]) -> copy of B 264 返回一個原字符串右對齊，并使用空格填充至長度width的新字符串 265 Return B right justified in a string of length width. Padding is 266 done using the specified fill character (default is a space) 267 """ 268 pass 269 270 def rpartition(self, sep): # real signature unknown; restored from __doc__ 271 """ 272 S.rpartition(sep) -> (head, sep, tail) 273 類似于partition()函數,不過是從右邊開始查找 274 Search for the separator sep in S, starting at the end of S, and return 275 the part before it, the separator itself, and the part after it. If the 276 separator is not found, return two empty strings and S. 277 """ 278 pass 279 280 def strip(self, chars=None): # real signature unknown; restored from __doc__ 281 """ 282 S.strip([chars]) -> str 283 刪除string字符串左右兩邊的空格、\n回車 284 Return a copy of the string S with leading and trailing 285 whitespace removed. 286 If chars is given and not None, remove characters in chars instead. 287 """ 288 return "" 289 290 def rstrip(self, *args, **kwargs): # real signature unknown 291 """ 292 Strip trailing bytes contained in the argument. 293 刪除string字符串末尾的空格 294 If the argument is omitted or None, strip trailing ASCII whitespace. 295 """ 296 pass 297 298 def lstrip(self, chars=None): # real signature unknown; restored from __doc__ 299 """ 300 S.lstrip([chars]) -> str 301 截掉string左邊的空格 302 Return a copy of the string S with leading whitespace removed. 303 If chars is given and not None, remove characters in chars instead. 304 """ 305 return "" 306 307 def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__ 308 """ 309 S.split(sep=None, maxsplit=-1) -> list of strings 310 以seq為分隔符切片string，與partition的區別結果不包含seq，如果maxsplit有指定值，僅分割maxsplit個字符串 311 Return a list of the words in S, using sep as the 312 delimiter string. If maxsplit is given, at most maxsplit 313 splits are done. If sep is not specified or is None, any 314 whitespace string is a separator and empty strings are 315 removed from the result. 316 """ 317 return [] 318 319 def rsplit(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__ 320 """ 321 S.rsplit(sep=None, maxsplit=-1) -> list of strings 322 323 Return a list of the words in S, using sep as the 324 delimiter string, starting at the end of the string and 325 working to the front. If maxsplit is given, at most maxsplit 326 splits are done. If sep is not specified, any whitespace string 327 is a separator. 328 """ 329 return [] 330 331 def splitlines(self, keepends=None): # real signature unknown; restored from __doc__ 332 """ 333 S.splitlines([keepends]) -> list of strings 334 按照行分隔，返回一個包含各行作為元素的列表 335 Return a list of the lines in S, breaking at line boundaries. 336 Line breaks are not included in the resulting list unless keepends 337 is given and true. 338 """ 339 return [] 340 341 def startswith(self, prefix, start=None, end=None): # real signature unknown; restored from __doc__ 342 """ 343 B.startswith(prefix[, start[, end]]) -> bool 344 檢查字符串是否是以prefix開頭，是則返回True，否則返回False。如果start和end指定值，則在指定范圍內檢查 345 Return True if B starts with the specified prefix, False otherwise. 346 With optional start, test B beginning at that position. 347 With optional end, stop comparing B at that position. 348 prefix can also be a tuple of bytes to try. 349 """ 350 return False 351 352 def swapcase(self): # real signature unknown; restored from __doc__ 353 """ 354 B.swapcase() -> copy of B 355 翻轉string中大小寫 356 Return a copy of B with uppercase ASCII characters converted 357 to lowercase ASCII and vice versa. 358 """ 359 pass 360 361 def title(self): # real signature unknown; restored from __doc__ 362 """ 363 S.title() -> str 364 返回“標題化”的string，就是說所有單詞都是以大寫開始，其余字母均為小寫 365 Return a titlecased version of S, i.e. words start with title case 366 characters, all remaining cased characters have lower case. 367 """ 368 return "" 369 370 def translate(self, table, deletechars=None): # real signature unknown; restored from __doc__ 371 """ 372 translate(table, [deletechars]) 373 根據table的表（包含256個字符）轉換string的字符，要過濾掉的字符放到deletechars參數中 374 Return a copy with each character mapped by the given translation table. 375 376 table 377 Translation table, which must be a bytes object of length 256. 378 379 All characters occurring in the optional argument deletechars are removed. 380 The remaining characters are mapped through the given translation table. 381 """ 382 pass 383 384 def upper(self): # real signature unknown; restored from __doc__ 385 """ 386 B.upper() -> copy of B 387 轉換string中的小寫字母為大寫 388 Return a copy of B with all ASCII characters converted to uppercase. 389 """ 390 pass 391 392 def zfill(self, width): # real signature unknown; restored from __doc__ 393 """ 394 B.zfill(width) -> copy of B 395 返回長度為width的字符串，原字符串string右對齊，前面填充0 396 Pad a numeric string B with zeros on the left, to fill a field 397 of the specified width. B is never truncated. 398 """ 399 pass 400 401 def format(self, *args, **kwargs): # known special case of str.format 402 """ 403 S.format(*args, **kwargs) -> str 404 405 Return a formatted version of S, using substitutions from args and kwargs. 406 The substitutions are identified by braces ('{' and '}'). 407 """ 408 pass 409 410 def format_map(self, mapping): # real signature unknown; restored from __doc__ 411 """ 412 S.format_map(mapping) -> str 413 414 Return a formatted version of S, using substitutions from mapping. 415 The substitutions are identified by braces ('{' and '}'). 416 """ 417 return "" 418 419 def isidentifier(self): # real signature unknown; restored from __doc__ 420 """ 421 S.isidentifier() -> bool 422 423 Return True if S is a valid identifier according 424 to the language definition. 425 426 Use keyword.iskeyword() to test for reserved identifiers 427 such as "def" and "class". 428 """ 429 return False View Code

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內建函數使用方法

1 >>> name = "wangeq" 2 >>> name.capitalize() #首字母大寫 3 'Wangeq' 4 >>> name.center(50,'-') #返回原字符串居中 5 '----------------------wangeq----------------------' 6 >>> len(name.center(50,'-')) 7 50 8 >>> hello ="welcome to beijing" 9 >>> hello.count('i') #計數i在string出現的次數 10 2 11 >>> hello.encode() #將字符串編碼成bytes格式 12 b'welcome to beijing' 13 >>> hello.endswith("ing") # 判斷字符串是否以 ing結尾 14 True 15 >>> hello.endswith("wl") 16 False 17 >>> 'wang\teq'.expandtabs() #輸出'wang eq'， 將\t轉換成多長的空格 18 'wang eq' 19 >>> hello.find('W') #查找W,找到返回其索引， 找不到返回-1 20 -1 21 >>> hello.find('w') 22 0 23 >>> 24 >>> 'wang12'.isalnum() #所有字符是否是字母或數字 25 True 26 >>> 'wang12#'.isalnum() 27 False 28 >>> 'wang12'.isalpha() #所有字符是否都是字母 29 False 30 >>> 'wang'.isalpha() 31 True 32 >>> '12345'.isdigit() #是否只包含十進制數字 33 True 34 >>> '0x122'.isdigit() 35 False 36 >>> ' '.isspace() #字符是否只包含空格 37 True 38 >>> 'Welcome To Beijing'.istitle() #是否標題化，首字母大寫 39 True 40 >>> '|'.join(['wangeq','jack','rose']) #以 ‘|’ 作為分隔符，將序列中字符合并為一個字符 41 'wangeq|jack|rose' 42 >>> hello.ljust(50,"-") #左對齊字符串，指定50個字符，以“-”填充空格 43 'welcome to beijing--------------------------------' 44 >>> hello.rjust(50,"-") #右對齊 45 '--------------------------------welcome to beijing' 46 >>> "WANGeq".lower() #轉換為小寫 47 'wangeq' 48 >>> 'welcome to beijing'.replace('to','TO') #TO替換to 49 'welcome TO beijing' 50 >>> 'welcome to beijing'.index('i') #查找‘c’ 下標位置，從左開始 51 13 52 >>> 'welcome to beijing'.rindex('i') #查找‘c’ 下標位置，從右開始 53 15 54 >>> ' wang \n'.strip() #去掉字符串左右空格 55 'wang' 56 >>> ' wang \n'.rstrip() 57 ' wang' 58 >>> ' wang \n'.lstrip() 59 'wang \n' 60 >>> 'WangisDDD'.swapcase() #翻轉大小寫字母 61 'wANGISddd' 62 >>> 'WNSNsssd ddd'.upper() #翻轉字符串中小寫為大寫 63 'WNSNSSSD DDD' 64 >>> 'wangeq'.zfill(50) #返回長度為50字符串右對齊，前面填充0 65 '00000000000000000000000000000000000000000000wangeq' 66 format: 67 >>> msg = "my name is {},and age is {}" 68 >>> msg.format("wange",23) 69 'my name is wange,and age is 23' 70 >>> msg = "my name is {0},and age is {1}" 71 >>> msg.format("wange",24) 72 'my name is wangeq,and age is 24' 73 >>> msg = "my name is {name},and age is {age}" 74 >>> msg.format(age=23,name="wange") 75 'my name is wange,and age is 23' 76 format_map: 77 >>> msg = "my name is {name},and age is {age}" 78 >>> msg.format_map({'name':'wangeq','age':22}) 79 'my name is wangeq,and age is 22' 80 maketrans: 81 >>> intab = 'abcdef' 82 >>> outtab = '123456' 83 >>> trantab = str.maketrans(intab, outtab) 84 >>> str = "this is string example...." 85 >>> str.translate(trantab) 86 'this is string 5x1mpl5....' 87 >>> 88 >>> c = "wangeq_ssdd" #檢測一段字符串可否被當作標志符，即是否符合變量命名規則 89 >>> c.isidentifier() 90 True

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轉載于:https://www.cnblogs.com/wangeq/p/6289639.html

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