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的字符串属性函数
- python的string模块
- 字符串属性函数
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