牛人总结python中string模块各属性以及函数的用法,果断转了,好东西
2013-01-25 17:00
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原文链接:http://blog.chinaunix.net/uid-25992400-id-3283846.html
任何语言都离不开字符,那就会涉及对字符的操作,尤其是脚本语言更是频繁,不管是生产环境还是面试考验都要面对字符串的操作。
python的字符串操作通过2部分的方法函数基本上就可以解决所有的字符串操作需求:
python的字符串属性函数
python的string模块
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
字符串属性函数
系统版本:CentOS release 6.2 (Final)2.6.32-220.el6.x86_64
python版本:Python 2.6.6
字符串属性方法
字符串格式输出对齐
大小写转换
字符串条件判断
字符串搜索定位与替换
字符串编码与解码
字符串分割变换
string模块源代码
任何语言都离不开字符,那就会涉及对字符的操作,尤其是脚本语言更是频繁,不管是生产环境还是面试考验都要面对字符串的操作。
python的字符串操作通过2部分的方法函数基本上就可以解决所有的字符串操作需求:
python的字符串属性函数
python的string模块
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
字符串属性函数
系统版本:CentOS release 6.2 (Final)2.6.32-220.el6.x86_64
python版本:Python 2.6.6
字符串属性方法
字符串格式输出对齐
1.>>> str='stRINg lEArn' 2.>>> 3.>>> str.center(20) #生成20个字符长度,str排中间 4.' stRINg lEArn ' 5.>>> 6.>>> str.ljust(20) #str左对齐 7.'stRINg lEArn ' 8.>>> 9.>>> str.rjust(20) #str右对齐 10.' stRINg lEArn' 11.>>> 12.>>> str.zfill(20) #str右对齐,左边填充0 13.'00000000stRINg lEArn'
大小写转换
1.>>> str='stRINg lEArn' 2.>>> 3.>>> str.upper() #转大写 4.'STRING LEARN' 5.>>> 6.>>> str.lower() #转小写 7.'string learn' 8.>>> 9.>>> str.capitalize() #字符串首为大写,其余小写 10.'String learn' 11.>>> 12.>>> str.swapcase() #大小写对换 13.'STrinG LeaRN' 14.>>> 15.>>> str.title() #以分隔符为标记,首字符为大写,其余为小写 16.'String Learn'
字符串条件判断
1.>>> str='0123' 2.>>> str.isalnum() #是否全是字母和数字,并至少有一个字符 3.True 4.>>> str.isdigit() #是否全是数字,并至少有一个字符 5.True 6. 7.>>> str='abcd' 8.>>> str.isalnum() 9.True 10.>>> str.isalpha() #是否全是字母,并至少有一个字符 11.True 12.>>> str.islower() #是否全是小写,当全是小写和数字一起时候,也判断为True 13.True 14. 15.>>> str='abcd0123' 16.>>> str.islower() #同上 17.True 18.>>> str.isalnum() 19.True 20. 21.>>> str=' ' 22.>>> str.isspace() #是否全是空白字符,并至少有一个字符 23.True 24.>>> str='ABC' 25.>>> str.isupper() #是否全是大写,当全是大写和数字一起时候,也判断为True 26.True 27.>>> str='Abb Acc' 28.>>> str.istitle() #所有单词字首都是大写,标题 29.True 30. 31.>>> str='string learn' 32.>>> str.startswith('str') #判断字符串以'str'开头 33.True 34.>>> str.endswith('arn') #判读字符串以'arn'结尾 35.True
字符串搜索定位与替换
1.>>> str='string lEARn' 2.>>> 3.>>> str.find('a') #查找字符串,没有则返回-1,有则返回查到到第一个匹配的索引 4.-1 5.>>> str.find('n') 6.4 7.>>> str.rfind('n') #同上,只是返回的索引是最后一次匹配的 8.11 9.>>> 10.>>> str.index('a') #如果没有匹配则报错 11.Traceback (most recent call last): 12. File "<stdin>", line 1, in <module> 13.ValueError: substring not found 14.>>> str.index('n') #同find类似,返回第一次匹配的索引值 15.4 16.>>> str.rindex('n') #返回最后一次匹配的索引值 17.11 18.>>> 19.>>> str.count('a') #字符串中匹配的次数 20.0 21.>>> str.count('n') #同上 22.2 23.>>> 24.>>> str.replace('EAR','ear') #匹配替换 25.'string learn' 26.>>> str.replace('n','N') 27.'striNg lEARN' 28.>>> str.replace('n','N',1) 29.'striNg lEARn' 30.>>> 31.>>> 32.>>> str.strip('n') #删除字符串首尾匹配的字符,通常用于默认删除回车符 33.'string lEAR' 34.>>> str.lstrip('n') #左匹配 35.'string lEARn' 36.>>> str.rstrip('n') #右匹配 37.'string lEAR' 38.>>> 39.>>> str=' tab' 40.>>> str.expandtabs() #把制表符转为空格 41.' tab' 42.>>> str.expandtabs(2) #指定空格数 43.' tab'
字符串编码与解码
1.>>> str='字符串学习' 2.>>> str 3.'xe5xadx97xe7xacxa6xe4xb8xb2xe5xadxa6xe4xb9xa0' 4.>>> 5.>>> str.decode('utf-8') #解码过程,将utf-8解码为unicode 6.u'u5b57u7b26u4e32u5b66u4e60' 7. 8.>>> str.decode('utf-8').encode('gbk') #编码过程,将unicode编码为gbk 9.'xd7xd6xb7xfbxb4xaexd1xa7xcfxb0' 10.>>> str.decode('utf-8').encode('utf-8') #将unicode编码为utf-8 11.'xe5xadx97xe7xacxa6xe4xb8xb2xe5xadxa6xe4xb9xa0'
字符串分割变换
1.>>> str='Learn string' 2.>>> '-'.join(str) 3.'L-e-a-r-n- -s-t-r-i-n-g' 4.>>> l1=['Learn','string'] 5.>>> '-'.join(l1) 6.'Learn-string' 7.>>> 8.>>> str.split('n') 9.['Lear', ' stri', 'g'] 10.>>> str.split('n',1) 11.['Lear', ' string'] 12.>>> str.rsplit('n',1) 13.['Learn stri', 'g'] 14.>>> 15.>>> str.splitlines() 16.['Learn string'] 17.>>> 18.>>> str.partition('n') 19.('Lear', 'n', ' string') 20.>>> str.rpartition('n') 21.('Learn stri', 'n', 'g')
string模块源代码
1."""A collection of string operations (most are no longer used). 2. 3.Warning: most of the code you see here isn't normally used nowadays. 4.Beginning with Python 1.6, many of these functions are implemented as 5.methods on the standard string object. They used to be implemented by 6.a built-in module called strop, but strop is now obsolete itself. 7. 8.Public module variables: 9. 10.whitespace -- a string containing all characters considered whitespace 11.lowercase -- a string containing all characters considered lowercase letters 12.uppercase -- a string containing all characters considered uppercase letters 13.letters -- a string containing all characters considered letters 14.digits -- a string containing all characters considered decimal digits 15.hexdigits -- a string containing all characters considered hexadecimal digits 16.octdigits -- a string containing all characters considered octal digits 17.punctuation -- a string containing all characters considered punctuation 18.printable -- a string containing all characters considered printable 19. 20.""" 21. 22.# Some strings for ctype-style character classification 23.whitespace = ' tnrvf' 24.lowercase = 'abcdefghijklmnopqrstuvwxyz' 25.uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' 26.letters = lowercase + uppercase 27.ascii_lowercase = lowercase 28.ascii_uppercase = uppercase 29.ascii_letters = ascii_lowercase + ascii_uppercase 30.digits = '0123456789' 31.hexdigits = digits + 'abcdef' + 'ABCDEF' 32.octdigits = '01234567' 33.punctuation = """!"#$%&'()*+,-./:;<=>?@[]^_`{|}~""" 34.printable = digits + letters + punctuation + whitespace 35. 36.# Case conversion helpers 37.# Use str to convert Unicode literal in case of -U 38.l = map(chr, xrange(256)) 39._idmap = str('').join(l) 40.del l 41. 42.# Functions which aren't available as string methods. 43. 44.# Capitalize the words in a string, e.g. " aBc dEf " -> "Abc Def". 45.def capwords(s, sep=None): 46. """capwords(s [,sep]) -> string 47. 48. Split the argument into words using split, capitalize each 49. word using capitalize, and join the capitalized words using 50. join. If the optional second argument sep is absent or None, 51. runs of whitespace characters are replaced by a single space 52. and leading and trailing whitespace are removed, otherwise 53. sep is used to split and join the words. 54. 55. """ 56. return (sep or ' ').join(x.capitalize() for x in s.split(sep)) 57. 58. 59.# Construct a translation string 60._idmapL = None 61.def maketrans(fromstr, tostr): 62. """maketrans(frm, to) -> string 63. 64. Return a translation table (a string of 256 bytes long) 65. suitable for use in string.translate. The strings frm and to 66. must be of the same length. 67. 68. """ 69. if len(fromstr) != len(tostr): 70. raise ValueError, "maketrans arguments must have same length" 71. global _idmapL 72. if not _idmapL: 73. _idmapL = list(_idmap) 74. L = _idmapL[:] 75. fromstr = map(ord, fromstr) 76. for i in range(len(fromstr)): 77. L[fromstr[i]] = tostr[i] 78. return ''.join(L) 79. 80. 81. 82.#################################################################### 83.import re as _re 84. 85.class _multimap: 86. """Helper class for combining multiple mappings. 87. 88. Used by .{safe_,}substitute() to combine the mapping and keyword 89. arguments. 90. """ 91. def __init__(self, primary, secondary): 92. self._primary = primary 93. self._secondary = secondary 94. 95. def __getitem__(self, key): 96. try: 97. return self._primary[key] 98. except KeyError: 99. return self._secondary[key] 100. 101. 102.class _TemplateMetaclass(type): 103. pattern = r""" 104. %(delim)s(?: 105. (?P<escaped>%(delim)s) | # Escape sequence of two delimiters 106. (?P<named>%(id)s) | # delimiter and a Python identifier 107. {(?P<braced>%(id)s)} | # delimiter and a braced identifier 108. (?P<invalid>) # Other ill-formed delimiter exprs 109. ) 110. """ 111. 112. def __init__(cls, name, bases, dct): 113. super(_TemplateMetaclass, cls).__init__(name, bases, dct) 114. if 'pattern' in dct: 115. pattern = cls.pattern 116. else: 117. pattern = _TemplateMetaclass.pattern % { 118. 'delim' : _re.escape(cls.delimiter), 119. 'id' : cls.idpattern, 120. } 121. cls.pattern = _re.compile(pattern, _re.IGNORECASE | _re.VERBOSE) 122. 123. 124.class Template: 125. """A string class for supporting $-substitutions.""" 126. __metaclass__ = _TemplateMetaclass 127. 128. delimiter = '$' 129. idpattern = r'[_a-z][_a-z0-9]*' 130. 131. def __init__(self, template): 132. self.template = template 133. 134. # Search for $$, $identifier, ${identifier}, and any bare $'s 135. 136. def _invalid(self, mo): 137. i = mo.start('invalid') 138. lines = self.template[:i].splitlines(True) 139. if not lines: 140. colno = 1 141. lineno = 1 142. else: 143. colno = i - len(''.join(lines[:-1])) 144. lineno = len(lines) 145. raise ValueError('Invalid placeholder in string: line %d, col %d' % 146. (lineno, colno)) 147. 148. def substitute(self, *args, **kws): 149. if len(args) > 1: 150. raise TypeError('Too many positional arguments') 151. if not args: 152. mapping = kws 153. elif kws: 154. mapping = _multimap(kws, args[0]) 155. else: 156. mapping = args[0] 157. # Helper function for .sub() 158. def convert(mo): 159. # Check the most common path first. 160. named = mo.group('named') or mo.group('braced') 161. if named is not None: 162. val = mapping[named] 163. # We use this idiom instead of str() because the latter will 164. # fail if val is a Unicode containing non-ASCII characters. 165. return '%s' % (val,) 166. if mo.group('escaped') is not None: 167. return self.delimiter 168. if mo.group('invalid') is not None: 169. self._invalid(mo) 170. raise ValueError('Unrecognized named group in pattern', 171. self.pattern) 172. return self.pattern.sub(convert, self.template) 173. 174. def safe_substitute(self, *args, **kws): 175. if len(args) > 1: 176. raise TypeError('Too many positional arguments') 177. if not args: 178. mapping = kws 179. elif kws: 180. mapping = _multimap(kws, args[0]) 181. else: 182. mapping = args[0] 183. # Helper function for .sub() 184. def convert(mo): 185. named = mo.group('named') 186. if named is not None: 187. try: 188. # We use this idiom instead of str() because the latter 189. # will fail if val is a Unicode containing non-ASCII 190. return '%s' % (mapping[named],) 191. except KeyError: 192. return self.delimiter + named 193. braced = mo.group('braced') 194. if braced is not None: 195. try: 196. return '%s' % (mapping[braced],) 197. except KeyError: 198. return self.delimiter + '{' + braced + '}' 199. if mo.group('escaped') is not None: 200. return self.delimiter 201. if mo.group('invalid') is not None: 202. return self.delimiter 203. raise ValueError('Unrecognized named group in pattern', 204. self.pattern) 205. return self.pattern.sub(convert, self.template) 206. 207. 208. 209.#################################################################### 210.# NOTE: Everything below here is deprecated. Use string methods instead. 211.# This stuff will go away in Python 3.0. 212. 213.# Backward compatible names for exceptions 214.index_error = ValueError 215.atoi_error = ValueError 216.atof_error = ValueError 217.atol_error = ValueError 218. 219.# convert UPPER CASE letters to lower case 220.def lower(s): 221. """lower(s) -> string 222. 223. Return a copy of the string s converted to lowercase. 224. 225. """ 226. return s.lower() 227. 228.# Convert lower case letters to UPPER CASE 229.def upper(s): 230. """upper(s) -> string 231. 232. Return a copy of the string s converted to uppercase. 233. 234. """ 235. return s.upper() 236. 237.# Swap lower case letters and UPPER CASE 238.def swapcase(s): 239. """swapcase(s) -> string 240. 241. Return a copy of the string s with upper case characters 242. converted to lowercase and vice versa. 243. 244. """ 245. return s.swapcase() 246. 247.# Strip leading and trailing tabs and spaces 248.def strip(s, chars=None): 249. """strip(s [,chars]) -> string 250. 251. Return a copy of the string s with leading and trailing 252. whitespace removed. 253. If chars is given and not None, remove characters in chars instead. 254. If chars is unicode, S will be converted to unicode before stripping. 255. 256. """ 257. return s.strip(chars) 258. 259.# Strip leading tabs and spaces 260.def lstrip(s, chars=None): 261. """lstrip(s [,chars]) -> string 262. 263. Return a copy of the string s with leading whitespace removed. 264. If chars is given and not None, remove characters in chars instead. 265. 266. """ 267. return s.lstrip(chars) 268. 269.# Strip trailing tabs and spaces 270.def rstrip(s, chars=None): 271. """rstrip(s [,chars]) -> string 272. 273. Return a copy of the string s with trailing whitespace removed. 274. If chars is given and not None, remove characters in chars instead. 275. 276. """ 277. return s.rstrip(chars) 278. 279. 280.# Split a string into a list of space/tab-separated words 281.def split(s, sep=None, maxsplit=-1): 282. """split(s [,sep [,maxsplit]]) -> list of strings 283. 284. Return a list of the words in the string s, using sep as the 285. delimiter string. If maxsplit is given, splits at no more than 286. maxsplit places (resulting in at most maxsplit+1 words). If sep 287. is not specified or is None, any whitespace string is a separator. 288. 289. (split and splitfields are synonymous) 290. 291. """ 292. return s.split(sep, maxsplit) 293.splitfields = split 294. 295.# Split a string into a list of space/tab-separated words 296.def rsplit(s, sep=None, maxsplit=-1): 297. """rsplit(s [,sep [,maxsplit]]) -> list of strings 298. 299. Return a list of the words in the string s, using sep as the 300. delimiter string, starting at the end of the string and working 301. to the front. If maxsplit is given, at most maxsplit splits are 302. done. If sep is not specified or is None, any whitespace string 303. is a separator. 304. """ 305. return s.rsplit(sep, maxsplit) 306. 307.# Join fields with optional separator 308.def join(words, sep = ' '): 309. """join(list [,sep]) -> string 310. 311. Return a string composed of the words in list, with 312. intervening occurrences of sep. The default separator is a 313. single space. 314. 315. (joinfields and join are synonymous) 316. 317. """ 318. return sep.join(words) 319.joinfields = join 320. 321.# Find substring, raise exception if not found 322.def index(s, *args): 323. """index(s, sub [,start [,end]]) -> int 324. 325. Like find but raises ValueError when the substring is not found. 326. 327. """ 328. return s.index(*args) 329. 330.# Find last substring, raise exception if not found 331.def rindex(s, *args): 332. """rindex(s, sub [,start [,end]]) -> int 333. 334. Like rfind but raises ValueError when the substring is not found. 335. 336. """ 337. return s.rindex(*args) 338. 339.# Count non-overlapping occurrences of substring 340.def count(s, *args): 341. """count(s, sub[, start[,end]]) -> int 342. 343. Return the number of occurrences of substring sub in string 344. s[start:end]. Optional arguments start and end are 345. interpreted as in slice notation. 346. 347. """ 348. return s.count(*args) 349. 350.# Find substring, return -1 if not found 351.def find(s, *args): 352. """find(s, sub [,start [,end]]) -> in 353. 354. Return the lowest index in s where substring sub is found, 355. such that sub is contained within s[start,end]. Optional 356. arguments start and end are interpreted as in slice notation. 357. 358. Return -1 on failure. 359. 360. """ 361. return s.find(*args) 362. 363.# Find last substring, return -1 if not found 364.def rfind(s, *args): 365. """rfind(s, sub [,start [,end]]) -> int 366. 367. Return the highest index in s where substring sub is found, 368. such that sub is contained within s[start,end]. Optional 369. arguments start and end are interpreted as in slice notation. 370. 371. Return -1 on failure. 372. 373. """ 374. return s.rfind(*args) 375. 376.# for a bit of speed 377._float = float 378._int = int 379._long = long 380. 381.# Convert string to float 382.def atof(s): 383. """atof(s) -> float 384. 385. Return the floating point number represented by the string s. 386. 387. """ 388. return _float(s) 389. 390. 391.# Convert string to integer 392.def atoi(s , base=10): 393. """atoi(s [,base]) -> int 394. 395. Return the integer represented by the string s in the given 396. base, which defaults to 10. The string s must consist of one 397. or more digits, possibly preceded by a sign. If base is 0, it 398. is chosen from the leading characters of s, 0 for octal, 0x or 399. 0X for hexadecimal. If base is 16, a preceding 0x or 0X is 400. accepted. 401. 402. """ 403. return _int(s, base) 404. 405. 406.# Convert string to long integer 407.def atol(s, base=10): 408. """atol(s [,base]) -> long 409. 410. Return the long integer represented by the string s in the 411. given base, which defaults to 10. The string s must consist 412. of one or more digits, possibly preceded by a sign. If base 413. is 0, it is chosen from the leading characters of s, 0 for 414. octal, 0x or 0X for hexadecimal. If base is 16, a preceding 415. 0x or 0X is accepted. A trailing L or l is not accepted, 416. unless base is 0. 417. 418. """ 419. return _long(s, base) 420. 421. 422.# Left-justify a string 423.def ljust(s, width, *args): 424. """ljust(s, width[, fillchar]) -> string 425. 426. Return a left-justified version of s, in a field of the 427. specified width, padded with spaces as needed. The string is 428. never truncated. If specified the fillchar is used instead of spaces. 429. 430. """ 431. return s.ljust(width, *args) 432. 433.# Right-justify a string 434.def rjust(s, width, *args): 435. """rjust(s, width[, fillchar]) -> string 436. 437. Return a right-justified version of s, in a field of the 438. specified width, padded with spaces as needed. The string is 439. never truncated. If specified the fillchar is used instead of spaces. 440. 441. """ 442. return s.rjust(width, *args) 443. 444.# Center a string 445.def center(s, width, *args): 446. """center(s, width[, fillchar]) -> string 447. 448. Return a center version of s, in a field of the specified 449. width. padded with spaces as needed. The string is never 450. truncated. If specified the fillchar is used instead of spaces. 451. 452. """ 453. return s.center(width, *args) 454. 455.# Zero-fill a number, e.g., (12, 3) --> '012' and (-3, 3) --> '-03' 456.# Decadent feature: the argument may be a string or a number 457.# (Use of this is deprecated; it should be a string as with ljust c.s.) 458.def zfill(x, width): 459. """zfill(x, width) -> string 460. 461. Pad a numeric string x with zeros on the left, to fill a field 462. of the specified width. The string x is never truncated. 463. 464. """ 465. if not isinstance(x, basestring): 466. x = repr(x) 467. return x.zfill(width) 468. 469.# Expand tabs in a string. 470.# Doesn't take non-printing chars into account, but does understand n. 471.def expandtabs(s, tabsize=8): 472. """expandtabs(s [,tabsize]) -> string 473. 474. Return a copy of the string s with all tab characters replaced 475. by the appropriate number of spaces, depending on the current 476. column, and the tabsize (default 8). 477. 478. """ 479. return s.expandtabs(tabsize) 480. 481.# Character translation through look-up table. 482.def translate(s, table, deletions=""): 483. """translate(s,table [,deletions]) -> string 484. 485. Return a copy of the string s, where all characters occurring 486. in the optional argument deletions are removed, and the 487. remaining characters have been mapped through the given 488. translation table, which must be a string of length 256. The 489. deletions argument is not allowed for Unicode strings. 490. 491. """ 492. if deletions or table is None: 493. return s.translate(table, deletions) 494. else: 495. # Add s[:0] so that if s is Unicode and table is an 8-bit string, 496. # table is converted to Unicode. This means that table *cannot* 497. # be a dictionary -- for that feature, use u.translate() directly. 498. return s.translate(table + s[:0]) 499. 500.# Capitalize a string, e.g. "aBc dEf" -> "Abc def". 501.def capitalize(s): 502. """capitalize(s) -> string 503. 504. Return a copy of the string s with only its first character 505. capitalized. 506. 507. """ 508. return s.capitalize() 509. 510.# Substring replacement (global) 511.def replace(s, old, new, maxsplit=-1): 512. """replace (str, old, new[, maxsplit]) -> string 513. 514. Return a copy of string str with all occurrences of substring 515. old replaced by new. If the optional argument maxsplit is 516. given, only the first maxsplit occurrences are replaced. 517. 518. """ 519. return s.replace(old, new, maxsplit) 520. 521. 522.# Try importing optional built-in module "strop" -- if it exists, 523.# it redefines some string operations that are 100-1000 times faster. 524.# It also defines values for whitespace, lowercase and uppercase 525.# that match <ctype.h>'s definitions. 526. 527.try: 528. from strop import maketrans, lowercase, uppercase, whitespace 529. letters = lowercase + uppercase 530.except ImportError: 531. pass # Use the original versions 532. 533.######################################################################## 534.# the Formatter class 535.# see PEP 3101 for details and purpose of this class 536. 537.# The hard parts are reused from the C implementation. They're exposed as "_" 538.# prefixed methods of str and unicode. 539. 540.# The overall parser is implemented in str._formatter_parser. 541.# The field name parser is implemented in str._formatter_field_name_split 542. 543.class Formatter(object): 544. def format(self, format_string, *args, **kwargs): 545. return self.vformat(format_string, args, kwargs) 546. 547. def vformat(self, format_string, args, kwargs): 548. used_args = set() 549. result = self._vformat(format_string, args, kwargs, used_args, 2) 550. self.check_unused_args(used_args, args, kwargs) 551. return result 552. 553. def _vformat(self, format_string, args, kwargs, used_args, recursion_depth): 554. if recursion_depth < 0: 555. raise ValueError('Max string recursion exceeded') 556. result = [] 557. for literal_text, field_name, format_spec, conversion in 558. self.parse(format_string): 559. 560. # output the literal text 561. if literal_text: 562. result.append(literal_text) 563. 564. # if there's a field, output it 565. if field_name is not None: 566. # this is some markup, find the object and do 567. # the formatting 568. 569. # given the field_name, find the object it references 570. # and the argument it came from 571. obj, arg_used = self.get_field(field_name, args, kwargs) 572. used_args.add(arg_used) 573. 574. # do any conversion on the resulting object 575. obj = self.convert_field(obj, conversion) 576. 577. # expand the format spec, if needed 578. format_spec = self._vformat(format_spec, args, kwargs, 579. used_args, recursion_depth-1) 580. 581. # format the object and append to the result 582. result.append(self.format_field(obj, format_spec)) 583. 584. return ''.join(result) 585. 586. 587. def get_value(self, key, args, kwargs): 588. if isinstance(key, (int, long)): 589. return args[key] 590. else: 591. return kwargs[key] 592. 593. 594. def check_unused_args(self, used_args, args, kwargs): 595. pass 596. 597. 598. def format_field(self, value, format_spec): 599. return format(value, format_spec) 600. 601. 602. def convert_field(self, value, conversion): 603. # do any conversion on the resulting object 604. if conversion == 'r': 605. return repr(value) 606. elif conversion == 's': 607. return str(value) 608. elif conversion is None: 609. return value 610. raise ValueError("Unknown converion specifier {0!s}".format(conversion)) 611. 612. 613. # returns an iterable that contains tuples of the form: 614. # (literal_text, field_name, format_spec, conversion) 615. # literal_text can be zero length 616. # field_name can be None, in which case there's no 617. # object to format and output 618. # if field_name is not None, it is looked up, formatted 619. # with format_spec and conversion and then used 620. def parse(self, format_string): 621. return format_string._formatter_parser() 622. 623. 624. # given a field_name, find the object it references. 625. # field_name: the field being looked up, e.g. "0.name" 626. # or "lookup[3]" 627. # used_args: a set of which args have been used 628. # args, kwargs: as passed in to vformat 629. def get_field(self, field_name, args, kwargs): 630. first, rest = field_name._formatter_field_name_split() 631. 632. obj = self.get_value(first, args, kwargs) 633. 634. # loop through the rest of the field_name, doing 635. # getattr or getitem as needed 636. for is_attr, i in rest: 637. if is_attr: 638. obj = getattr(obj, i) 639. else: 640. obj = obj[i] 641. 642. return obj, first
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