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 "", line 1, in

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%(delim)s) | # Escape sequence of two delimiters

106. (?P%(id)s) | # delimiter and a Python identifier

107. {(?P%(id)s)} | # delimiter and a braced identifier

108. (?P) # 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 '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