python字符串输出代码_Python 字符串操作及string模块使用

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 as5 methods on the standard string object. They used to be implemented by6 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 whitespace11 lowercase -- a string containing all characters considered lowercase letters12 uppercase -- a string containing all characters considered uppercase letters13 letters -- a string containing all characters considered letters14 digits -- a string containing all characters considered decimal digits15 hexdigits -- a string containing all characters considered hexadecimal digits16 octdigits -- a string containing all characters considered octal digits17 punctuation -- a string containing all characters considered punctuation18 printable -- a string containing all characters considered printable19

20 """

21

22 #Some strings for ctype-style character classification

23 whitespace = '\t\n\r\v\f'

24 lowercase = 'abcdefghijklmnopqrstuvwxyz'

25 uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

26 letters = lowercase +uppercase27 ascii_lowercase =lowercase28 ascii_uppercase =uppercase29 ascii_letters = ascii_lowercase +ascii_uppercase30 digits = '0123456789'

31 hexdigits = digits + 'abcdef' + 'ABCDEF'

32 octdigits = '01234567'

33 punctuation = """!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~"""

34 printable = digits + letters + punctuation +whitespace35

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 dell41

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]) -> string47

48 Split the argument into words using split, capitalize each49 word using capitalize, and join the capitalized words using50 join. If the optional second argument sep is absent or None,51 runs of whitespace characters are replaced by a single space52 and leading and trailing whitespace are removed, otherwise53 sep is used to split and join the words.54

55 """

56 return (sep or ' ').join(x.capitalize() for x ins.split(sep))57

58

59 #Construct a translation string

60 _idmapL =None61 defmaketrans(fromstr, tostr):62 """maketrans(frm, to) -> string63

64 Return a translation table (a string of 256 bytes long)65 suitable for use in string.translate. The strings frm and to66 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_idmapL72 if not_idmapL:73 _idmapL =list(_idmap)74 L =_idmapL[:]75 fromstr =map(ord, fromstr)76 for i inrange(len(fromstr)):77 L[fromstr[i]] =tostr[i]78 return ''.join(L)79

80

81

82 ####################################################################

83 importre as _re84

85 class_multimap:86 """Helper class for combining multiple mappings.87

88 Used by .{safe_,}substitute() to combine the mapping and keyword89 arguments.90 """

91 def __init__(self, primary, secondary):92 self._primary =primary93 self._secondary =secondary94

95 def __getitem__(self, key):96 try:97 returnself._primary[key]98 exceptKeyError:99 returnself._secondary[key]100

101

102 class_TemplateMetaclass(type):103 pattern = r"""

104 %(delim)s(?:105 (?P%(delim)s) | # Escape sequence of two delimiters106 (?P%(id)s) | # delimiter and a Python identifier107 {(?P%(id)s)} | # delimiter and a braced identifier108 (?P) # Other ill-formed delimiter exprs109 )110 """

111

112 def __init__(cls, name, bases, dct):113 super(_TemplateMetaclass, cls).__init__(name, bases, dct)114 if 'pattern' indct:115 pattern =cls.pattern116 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 classTemplate:125 """A string class for supporting $-substitutions."""

126 __metaclass__ =_TemplateMetaclass127

128 delimiter = '$'

129 idpattern = r'[_a-z][_a-z0-9]*'

130

131 def __init__(self, template):132 self.template =template133

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 notlines: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(*args, **kws):149 if notargs:150 raise TypeError("descriptor 'substitute' of 'Template' object"

151 "needs an argument")152 self, args = args[0], args[1:] #allow the "self" keyword be passed

153 if len(args) > 1:154 raise TypeError('Too many positional arguments')155 if notargs:156 mapping =kws157 elifkws:158 mapping =_multimap(kws, args[0])159 else:160 mapping =args[0]161 #Helper function for .sub()

162 defconvert(mo):163 #Check the most common path first.

164 named = mo.group('named') or mo.group('braced')165 if named is notNone:166 val =mapping[named]167 #We use this idiom instead of str() because the latter will

168 #fail if val is a Unicode containing non-ASCII characters.

169 return '%s' %(val,)170 if mo.group('escaped') is notNone:171 returnself.delimiter172 if mo.group('invalid') is notNone:173 self._invalid(mo)174 raise ValueError('Unrecognized named group in pattern',175 self.pattern)176 returnself.pattern.sub(convert, self.template)177

178 def safe_substitute(*args, **kws):179 if notargs:180 raise TypeError("descriptor 'safe_substitute' of 'Template' object"

181 "needs an argument")182 self, args = args[0], args[1:] #allow the "self" keyword be passed

183 if len(args) > 1:184 raise TypeError('Too many positional arguments')185 if notargs:186 mapping =kws187 elifkws:188 mapping =_multimap(kws, args[0])189 else:190 mapping =args[0]191 #Helper function for .sub()

192 defconvert(mo):193 named = mo.group('named') or mo.group('braced')194 if named is notNone:195 try:196 #We use this idiom instead of str() because the latter

197 #will fail if val is a Unicode containing non-ASCII

198 return '%s' %(mapping[named],)199 exceptKeyError:200 returnmo.group()201 if mo.group('escaped') is notNone:202 returnself.delimiter203 if mo.group('invalid') is notNone:204 returnmo.group()205 raise ValueError('Unrecognized named group in pattern',206 self.pattern)207 returnself.pattern.sub(convert, self.template)208

209

210

211 ####################################################################

212 #NOTE: Everything below here is deprecated. Use string methods instead.

213 #This stuff will go away in Python 3.0.

214

215 #Backward compatible names for exceptions

216 index_error =ValueError217 atoi_error =ValueError218 atof_error =ValueError219 atol_error =ValueError220

221 #convert UPPER CASE letters to lower case

222 deflower(s):223 """lower(s) -> string224

225 Return a copy of the string s converted to lowercase.226

227 """

228 returns.lower()229

230 #Convert lower case letters to UPPER CASE

231 defupper(s):232 """upper(s) -> string233

234 Return a copy of the string s converted to uppercase.235

236 """

237 returns.upper()238

239 #Swap lower case letters and UPPER CASE

240 defswapcase(s):241 """swapcase(s) -> string242

243 Return a copy of the string s with upper case characters244 converted to lowercase and vice versa.245

246 """

247 returns.swapcase()248

249 #Strip leading and trailing tabs and spaces

250 def strip(s, chars=None):251 """strip(s [,chars]) -> string252

253 Return a copy of the string s with leading and trailing254 whitespace removed.255 If chars is given and not None, remove characters in chars instead.256 If chars is unicode, S will be converted to unicode before stripping.257

258 """

259 returns.strip(chars)260

261 #Strip leading tabs and spaces

262 def lstrip(s, chars=None):263 """lstrip(s [,chars]) -> string264

265 Return a copy of the string s with leading whitespace removed.266 If chars is given and not None, remove characters in chars instead.267

268 """

269 returns.lstrip(chars)270

271 #Strip trailing tabs and spaces

272 def rstrip(s, chars=None):273 """rstrip(s [,chars]) -> string274

275 Return a copy of the string s with trailing whitespace removed.276 If chars is given and not None, remove characters in chars instead.277

278 """

279 returns.rstrip(chars)280

281

282 #Split a string into a list of space/tab-separated words

283 def split(s, sep=None, maxsplit=-1):284 """split(s [,sep [,maxsplit]]) -> list of strings285

286 Return a list of the words in the string s, using sep as the287 delimiter string. If maxsplit is given, splits at no more than288 maxsplit places (resulting in at most maxsplit+1 words). If sep289 is not specified or is None, any whitespace string is a separator.290

291 (split and splitfields are synonymous)292

293 """

294 returns.split(sep, maxsplit)295 splitfields =split296

297 #Split a string into a list of space/tab-separated words

298 def rsplit(s, sep=None, maxsplit=-1):299 """rsplit(s [,sep [,maxsplit]]) -> list of strings300

301 Return a list of the words in the string s, using sep as the302 delimiter string, starting at the end of the string and working303 to the front. If maxsplit is given, at most maxsplit splits are304 done. If sep is not specified or is None, any whitespace string305 is a separator.306 """

307 returns.rsplit(sep, maxsplit)308

309 #Join fields with optional separator

310 def join(words, sep = ' '):311 """join(list [,sep]) -> string312

313 Return a string composed of the words in list, with314 intervening occurrences of sep. The default separator is a315 single space.316

317 (joinfields and join are synonymous)318

319 """

320 returnsep.join(words)321 joinfields =join322

323 #Find substring, raise exception if not found

324 def index(s, *args):325 """index(s, sub [,start [,end]]) -> int326

327 Like find but raises ValueError when the substring is not found.328

329 """

330 return s.index(*args)331

332 #Find last substring, raise exception if not found

333 def rindex(s, *args):334 """rindex(s, sub [,start [,end]]) -> int335

336 Like rfind but raises ValueError when the substring is not found.337

338 """

339 return s.rindex(*args)340

341 #Count non-overlapping occurrences of substring

342 def count(s, *args):343 """count(s, sub[, start[,end]]) -> int344

345 Return the number of occurrences of substring sub in string346 s[start:end]. Optional arguments start and end are347 interpreted as in slice notation.348

349 """

350 return s.count(*args)351

352 #Find substring, return -1 if not found

353 def find(s, *args):354 """find(s, sub [,start [,end]]) -> in355

356 Return the lowest index in s where substring sub is found,357 such that sub is contained within s[start,end]. Optional358 arguments start and end are interpreted as in slice notation.359

360 Return -1 on failure.361

362 """

363 return s.find(*args)364

365 #Find last substring, return -1 if not found

366 def rfind(s, *args):367 """rfind(s, sub [,start [,end]]) -> int368

369 Return the highest index in s where substring sub is found,370 such that sub is contained within s[start,end]. Optional371 arguments start and end are interpreted as in slice notation.372

373 Return -1 on failure.374

375 """

376 return s.rfind(*args)377

378 #for a bit of speed

379 _float =float380 _int =int381 _long =long382

383 #Convert string to float

384 defatof(s):385 """atof(s) -> float386

387 Return the floating point number represented by the string s.388

389 """

390 return_float(s)391

392

393 #Convert string to integer

394 def atoi(s , base=10):395 """atoi(s [,base]) -> int396

397 Return the integer represented by the string s in the given398 base, which defaults to 10. The string s must consist of one399 or more digits, possibly preceded by a sign. If base is 0, it400 is chosen from the leading characters of s, 0 for octal, 0x or401 0X for hexadecimal. If base is 16, a preceding 0x or 0X is402 accepted.403

404 """

405 return_int(s, base)406

407

408 #Convert string to long integer

409 def atol(s, base=10):410 """atol(s [,base]) -> long411

412 Return the long integer represented by the string s in the413 given base, which defaults to 10. The string s must consist414 of one or more digits, possibly preceded by a sign. If base415 is 0, it is chosen from the leading characters of s, 0 for416 octal, 0x or 0X for hexadecimal. If base is 16, a preceding417 0x or 0X is accepted. A trailing L or l is not accepted,418 unless base is 0.419

420 """

421 return_long(s, base)422

423

424 #Left-justify a string

425 def ljust(s, width, *args):426 """ljust(s, width[, fillchar]) -> string427

428 Return a left-justified version of s, in a field of the429 specified width, padded with spaces as needed. The string is430 never truncated. If specified the fillchar is used instead of spaces.431

432 """

433 return s.ljust(width, *args)434

435 #Right-justify a string

436 def rjust(s, width, *args):437 """rjust(s, width[, fillchar]) -> string438

439 Return a right-justified version of s, in a field of the440 specified width, padded with spaces as needed. The string is441 never truncated. If specified the fillchar is used instead of spaces.442

443 """

444 return s.rjust(width, *args)445

446 #Center a string

447 def center(s, width, *args):448 """center(s, width[, fillchar]) -> string449

450 Return a center version of s, in a field of the specified451 width. padded with spaces as needed. The string is never452 truncated. If specified the fillchar is used instead of spaces.453

454 """

455 return s.center(width, *args)456

457 #Zero-fill a number, e.g., (12, 3) --> '012' and (-3, 3) --> '-03'

458 #Decadent feature: the argument may be a string or a number

459 #(Use of this is deprecated; it should be a string as with ljust c.s.)

460 defzfill(x, width):461 """zfill(x, width) -> string462

463 Pad a numeric string x with zeros on the left, to fill a field464 of the specified width. The string x is never truncated.465

466 """

467 if notisinstance(x, basestring):468 x =repr(x)469 returnx.zfill(width)470

471 #Expand tabs in a string.

472 #Doesn't take non-printing chars into account, but does understand \n.

473 def expandtabs(s, tabsize=8):474 """expandtabs(s [,tabsize]) -> string475

476 Return a copy of the string s with all tab characters replaced477 by the appropriate number of spaces, depending on the current478 column, and the tabsize (default 8).479

480 """

481 returns.expandtabs(tabsize)482

483 #Character translation through look-up table.

484 def translate(s, table, deletions=""):485 """translate(s,table [,deletions]) -> string486

487 Return a copy of the string s, where all characters occurring488 in the optional argument deletions are removed, and the489 remaining characters have been mapped through the given490 translation table, which must be a string of length 256. The491 deletions argument is not allowed for Unicode strings.492

493 """

494 if deletions or table isNone:495 returns.translate(table, deletions)496 else:497 #Add s[:0] so that if s is Unicode and table is an 8-bit string,

498 #table is converted to Unicode. This means that table *cannot*

499 #be a dictionary -- for that feature, use u.translate() directly.

500 return s.translate(table +s[:0])501

502 #Capitalize a string, e.g. "aBc dEf" -> "Abc def".

503 defcapitalize(s):504 """capitalize(s) -> string505

506 Return a copy of the string s with only its first character507 capitalized.508

509 """

510 returns.capitalize()511

512 #Substring replacement (global)

513 def replace(s, old, new, maxreplace=-1):514 """replace (str, old, new[, maxreplace]) -> string515

516 Return a copy of string str with all occurrences of substring517 old replaced by new. If the optional argument maxreplace is518 given, only the first maxreplace occurrences are replaced.519

520 """

521 returns.replace(old, new, maxreplace)522

523

524 #Try importing optional built-in module "strop" -- if it exists,

525 #it redefines some string operations that are 100-1000 times faster.

526 #It also defines values for whitespace, lowercase and uppercase

527 #that match 's definitions.

528

529 try:530 from strop importmaketrans, lowercase, uppercase, whitespace531 letters = lowercase +uppercase532 exceptImportError:533 pass #Use the original versions

534

535 ########################################################################

536 #the Formatter class

537 #see PEP 3101 for details and purpose of this class

538

539 #The hard parts are reused from the C implementation. They're exposed as "_"

540 #prefixed methods of str and unicode.

541

542 #The overall parser is implemented in str._formatter_parser.

543 #The field name parser is implemented in str._formatter_field_name_split

544

545 classFormatter(object):546 def format(*args, **kwargs):547 if notargs:548 raise TypeError("descriptor 'format' of 'Formatter' object"

549 "needs an argument")550 self, args = args[0], args[1:] #allow the "self" keyword be passed

551 try:552 format_string, args = args[0], args[1:] #allow the "format_string" keyword be passed

553 exceptIndexError:554 if 'format_string' inkwargs:555 format_string = kwargs.pop('format_string')556 else:557 raise TypeError("format() missing 1 required positional"

558 "argument: 'format_string'")559 returnself.vformat(format_string, args, kwargs)560

561 defvformat(self, format_string, args, kwargs):562 used_args =set()563 result = self._vformat(format_string, args, kwargs, used_args, 2)564 self.check_unused_args(used_args, args, kwargs)565 returnresult566

567 def_vformat(self, format_string, args, kwargs, used_args, recursion_depth):568 if recursion_depth <0:569 raise ValueError('Max string recursion exceeded')570 result =[]571 for literal_text, field_name, format_spec, conversion in\572 self.parse(format_string):573

574 #output the literal text

575 ifliteral_text:576 result.append(literal_text)577

578 #if there's a field, output it

579 if field_name is notNone:580 #this is some markup, find the object and do

581 #the formatting

582

583 #given the field_name, find the object it references

584 #and the argument it came from

585 obj, arg_used =self.get_field(field_name, args, kwargs)586 used_args.add(arg_used)587

588 #do any conversion on the resulting object

589 obj =self.convert_field(obj, conversion)590

591 #expand the format spec, if needed

592 format_spec =self._vformat(format_spec, args, kwargs,593 used_args, recursion_depth-1)594

595 #format the object and append to the result

596 result.append(self.format_field(obj, format_spec))597

598 return ''.join(result)599

600

601 defget_value(self, key, args, kwargs):602 ifisinstance(key, (int, long)):603 returnargs[key]604 else:605 returnkwargs[key]606

607

608 defcheck_unused_args(self, used_args, args, kwargs):609 pass

610

611

612 defformat_field(self, value, format_spec):613 returnformat(value, format_spec)614

615

616 defconvert_field(self, value, conversion):617 #do any conversion on the resulting object

618 if conversion isNone:619 returnvalue620 elif conversion == 's':621 returnstr(value)622 elif conversion == 'r':623 returnrepr(value)624 raise ValueError("Unknown conversion specifier {0!s}".format(conversion))625

626

627 #returns an iterable that contains tuples of the form:

628 #(literal_text, field_name, format_spec, conversion)

629 #literal_text can be zero length

630 #field_name can be None, in which case there's no

631 #object to format and output

632 #if field_name is not None, it is looked up, formatted

633 #with format_spec and conversion and then used

634 defparse(self, format_string):635 returnformat_string._formatter_parser()636

637

638 #given a field_name, find the object it references.

639 #field_name: the field being looked up, e.g. "0.name"

640 #or "lookup[3]"

641 #used_args: a set of which args have been used

642 #args, kwargs: as passed in to vformat

643 defget_field(self, field_name, args, kwargs):644 first, rest =field_name._formatter_field_name_split()645

646 obj =self.get_value(first, args, kwargs)647

648 #loop through the rest of the field_name, doing

649 #getattr or getitem as needed

650 for is_attr, i inrest:651 ifis_attr:652 obj =getattr(obj, i)653 else:654 obj =obj[i]655

656 return obj, first