AppPkg/Applications/Python/Python-2.7.10/Lib/textwrap.py

   1 """Text wrapping and filling.
   2 """
   3
   4 # Copyright (C) 1999-2001 Gregory P. Ward.
   5 # Copyright (C) 2002, 2003 Python Software Foundation.
   6 # Written by Greg Ward <gward@python.net>
   7
   8 __revision__ = "$Id$"
   9
  10 import string, re
  11
  12 try:
  13     _unicode = unicode
  14 except NameError:
  15     # If Python is built without Unicode support, the unicode type
  16     # will not exist. Fake one.
  17     class _unicode(object):
  18         pass
  19
  20 # Do the right thing with boolean values for all known Python versions
  21 # (so this module can be copied to projects that don't depend on Python
  22 # 2.3, e.g. Optik and Docutils) by uncommenting the block of code below.
  23 #try:
  24 #    True, False
  25 #except NameError:
  26 #    (True, False) = (1, 0)
  27
  28 __all__ = ['TextWrapper', 'wrap', 'fill', 'dedent']
  29
  30 # Hardcode the recognized whitespace characters to the US-ASCII
  31 # whitespace characters.  The main reason for doing this is that in
  32 # ISO-8859-1, 0xa0 is non-breaking whitespace, so in certain locales
  33 # that character winds up in string.whitespace.  Respecting
  34 # string.whitespace in those cases would 1) make textwrap treat 0xa0 the
  35 # same as any other whitespace char, which is clearly wrong (it's a
  36 # *non-breaking* space), 2) possibly cause problems with Unicode,
  37 # since 0xa0 is not in range(128).
  38 _whitespace = '\t\n\x0b\x0c\r '
  39
  40 class TextWrapper:
  41     """
  42     Object for wrapping/filling text.  The public interface consists of
  43     the wrap() and fill() methods; the other methods are just there for
  44     subclasses to override in order to tweak the default behaviour.
  45     If you want to completely replace the main wrapping algorithm,
  46     you'll probably have to override _wrap_chunks().
  47
  48     Several instance attributes control various aspects of wrapping:
  49       width (default: 70)
  50         the maximum width of wrapped lines (unless break_long_words
  51         is false)
  52       initial_indent (default: "")
  53         string that will be prepended to the first line of wrapped
  54         output.  Counts towards the line's width.
  55       subsequent_indent (default: "")
  56         string that will be prepended to all lines save the first
  57         of wrapped output; also counts towards each line's width.
  58       expand_tabs (default: true)
  59         Expand tabs in input text to spaces before further processing.
  60         Each tab will become 1 .. 8 spaces, depending on its position in
  61         its line.  If false, each tab is treated as a single character.
  62       replace_whitespace (default: true)
  63         Replace all whitespace characters in the input text by spaces
  64         after tab expansion.  Note that if expand_tabs is false and
  65         replace_whitespace is true, every tab will be converted to a
  66         single space!
  67       fix_sentence_endings (default: false)
  68         Ensure that sentence-ending punctuation is always followed
  69         by two spaces.  Off by default because the algorithm is
  70         (unavoidably) imperfect.
  71       break_long_words (default: true)
  72         Break words longer than 'width'.  If false, those words will not
  73         be broken, and some lines might be longer than 'width'.
  74       break_on_hyphens (default: true)
  75         Allow breaking hyphenated words. If true, wrapping will occur
  76         preferably on whitespaces and right after hyphens part of
  77         compound words.
  78       drop_whitespace (default: true)
  79         Drop leading and trailing whitespace from lines.
  80     """
  81
  82     whitespace_trans = string.maketrans(_whitespace, ' ' * len(_whitespace))
  83
  84     unicode_whitespace_trans = {}
  85     uspace = ord(u' ')
  86     for x in map(ord, _whitespace):
  87         unicode_whitespace_trans[x] = uspace
  88
  89     # This funky little regex is just the trick for splitting
  90     # text up into word-wrappable chunks.  E.g.
  91     #   "Hello there -- you goof-ball, use the -b option!"
  92     # splits into
  93     #   Hello/ /there/ /--/ /you/ /goof-/ball,/ /use/ /the/ /-b/ /option!
  94     # (after stripping out empty strings).
  95     wordsep_re = re.compile(
  96         r'(\s+|'                                  # any whitespace
  97         r'[^\s\w]*\w+[^0-9\W]-(?=\w+[^0-9\W])|'   # hyphenated words
  98         r'(?<=[\w\!\"\'\&\.\,\?])-{2,}(?=\w))')   # em-dash
  99
 100     # This less funky little regex just split on recognized spaces. E.g.
 101     #   "Hello there -- you goof-ball, use the -b option!"
 102     # splits into
 103     #   Hello/ /there/ /--/ /you/ /goof-ball,/ /use/ /the/ /-b/ /option!/
 104     wordsep_simple_re = re.compile(r'(\s+)')
 105
 106     # XXX this is not locale- or charset-aware -- string.lowercase
 107     # is US-ASCII only (and therefore English-only)
 108     sentence_end_re = re.compile(r'[%s]'              # lowercase letter
 109                                  r'[\.\!\?]'          # sentence-ending punct.
 110                                  r'[\"\']?'           # optional end-of-quote
 111                                  r'\Z'                # end of chunk
 112                                  % string.lowercase)
 113
 114
 115     def __init__(self,
 116                  width=70,
 117                  initial_indent="",
 118                  subsequent_indent="",
 119                  expand_tabs=True,
 120                  replace_whitespace=True,
 121                  fix_sentence_endings=False,
 122                  break_long_words=True,
 123                  drop_whitespace=True,
 124                  break_on_hyphens=True):
 125         self.width = width
 126         self.initial_indent = initial_indent
 127         self.subsequent_indent = subsequent_indent
 128         self.expand_tabs = expand_tabs
 129         self.replace_whitespace = replace_whitespace
 130         self.fix_sentence_endings = fix_sentence_endings
 131         self.break_long_words = break_long_words
 132         self.drop_whitespace = drop_whitespace
 133         self.break_on_hyphens = break_on_hyphens
 134
 135         # recompile the regexes for Unicode mode -- done in this clumsy way for
 136         # backwards compatibility because it's rather common to monkey-patch
 137         # the TextWrapper class' wordsep_re attribute.
 138         self.wordsep_re_uni = re.compile(self.wordsep_re.pattern, re.U)
 139         self.wordsep_simple_re_uni = re.compile(
 140             self.wordsep_simple_re.pattern, re.U)
 141
 142
 143     # -- Private methods -----------------------------------------------
 144     # (possibly useful for subclasses to override)
 145
 146     def _munge_whitespace(self, text):
 147         """_munge_whitespace(text : string) -> string
 148
 149         Munge whitespace in text: expand tabs and convert all other
 150         whitespace characters to spaces.  Eg. " foo\\tbar\\n\\nbaz"
 151         becomes " foo    bar  baz".
 152         """
 153         if self.expand_tabs:
 154             text = text.expandtabs()
 155         if self.replace_whitespace:
 156             if isinstance(text, str):
 157                 text = text.translate(self.whitespace_trans)
 158             elif isinstance(text, _unicode):
 159                 text = text.translate(self.unicode_whitespace_trans)
 160         return text
 161
 162
 163     def _split(self, text):
 164         """_split(text : string) -> [string]
 165
 166         Split the text to wrap into indivisible chunks.  Chunks are
 167         not quite the same as words; see _wrap_chunks() for full
 168         details.  As an example, the text
 169           Look, goof-ball -- use the -b option!
 170         breaks into the following chunks:
 171           'Look,', ' ', 'goof-', 'ball', ' ', '--', ' ',
 172           'use', ' ', 'the', ' ', '-b', ' ', 'option!'
 173         if break_on_hyphens is True, or in:
 174           'Look,', ' ', 'goof-ball', ' ', '--', ' ',
 175           'use', ' ', 'the', ' ', '-b', ' ', option!'
 176         otherwise.
 177         """
 178         if isinstance(text, _unicode):
 179             if self.break_on_hyphens:
 180                 pat = self.wordsep_re_uni
 181             else:
 182                 pat = self.wordsep_simple_re_uni
 183         else:
 184             if self.break_on_hyphens:
 185                 pat = self.wordsep_re
 186             else:
 187                 pat = self.wordsep_simple_re
 188         chunks = pat.split(text)
 189         chunks = filter(None, chunks)  # remove empty chunks
 190         return chunks
 191
 192     def _fix_sentence_endings(self, chunks):
 193         """_fix_sentence_endings(chunks : [string])
 194
 195         Correct for sentence endings buried in 'chunks'.  Eg. when the
 196         original text contains "... foo.\\nBar ...", munge_whitespace()
 197         and split() will convert that to [..., "foo.", " ", "Bar", ...]
 198         which has one too few spaces; this method simply changes the one
 199         space to two.
 200         """
 201         i = 0
 202         patsearch = self.sentence_end_re.search
 203         while i < len(chunks)-1:
 204             if chunks[i+1] == " " and patsearch(chunks[i]):
 205                 chunks[i+1] = "  "
 206                 i += 2
 207             else:
 208                 i += 1
 209
 210     def _handle_long_word(self, reversed_chunks, cur_line, cur_len, width):
 211         """_handle_long_word(chunks : [string],
 212                              cur_line : [string],
 213                              cur_len : int, width : int)
 214
 215         Handle a chunk of text (most likely a word, not whitespace) that
 216         is too long to fit in any line.
 217         """
 218         # Figure out when indent is larger than the specified width, and make
 219         # sure at least one character is stripped off on every pass
 220         if width < 1:
 221             space_left = 1
 222         else:
 223             space_left = width - cur_len
 224
 225         # If we're allowed to break long words, then do so: put as much
 226         # of the next chunk onto the current line as will fit.
 227         if self.break_long_words:
 228             cur_line.append(reversed_chunks[-1][:space_left])
 229             reversed_chunks[-1] = reversed_chunks[-1][space_left:]
 230
 231         # Otherwise, we have to preserve the long word intact.  Only add
 232         # it to the current line if there's nothing already there --
 233         # that minimizes how much we violate the width constraint.
 234         elif not cur_line:
 235             cur_line.append(reversed_chunks.pop())
 236
 237         # If we're not allowed to break long words, and there's already
 238         # text on the current line, do nothing.  Next time through the
 239         # main loop of _wrap_chunks(), we'll wind up here again, but
 240         # cur_len will be zero, so the next line will be entirely
 241         # devoted to the long word that we can't handle right now.
 242
 243     def _wrap_chunks(self, chunks):
 244         """_wrap_chunks(chunks : [string]) -> [string]
 245
 246         Wrap a sequence of text chunks and return a list of lines of
 247         length 'self.width' or less.  (If 'break_long_words' is false,
 248         some lines may be longer than this.)  Chunks correspond roughly
 249         to words and the whitespace between them: each chunk is
 250         indivisible (modulo 'break_long_words'), but a line break can
 251         come between any two chunks.  Chunks should not have internal
 252         whitespace; ie. a chunk is either all whitespace or a "word".
 253         Whitespace chunks will be removed from the beginning and end of
 254         lines, but apart from that whitespace is preserved.
 255         """
 256         lines = []
 257         if self.width <= 0:
 258             raise ValueError("invalid width %r (must be > 0)" % self.width)
 259
 260         # Arrange in reverse order so items can be efficiently popped
 261         # from a stack of chucks.
 262         chunks.reverse()
 263
 264         while chunks:
 265
 266             # Start the list of chunks that will make up the current line.
 267             # cur_len is just the length of all the chunks in cur_line.
 268             cur_line = []
 269             cur_len = 0
 270
 271             # Figure out which static string will prefix this line.
 272             if lines:
 273                 indent = self.subsequent_indent
 274             else:
 275                 indent = self.initial_indent
 276
 277             # Maximum width for this line.
 278             width = self.width - len(indent)
 279
 280             # First chunk on line is whitespace -- drop it, unless this
 281             # is the very beginning of the text (ie. no lines started yet).
 282             if self.drop_whitespace and chunks[-1].strip() == '' and lines:
 283                 del chunks[-1]
 284
 285             while chunks:
 286                 l = len(chunks[-1])
 287
 288                 # Can at least squeeze this chunk onto the current line.
 289                 if cur_len + l <= width:
 290                     cur_line.append(chunks.pop())
 291                     cur_len += l
 292
 293                 # Nope, this line is full.
 294                 else:
 295                     break
 296
 297             # The current line is full, and the next chunk is too big to
 298             # fit on *any* line (not just this one).
 299             if chunks and len(chunks[-1]) > width:
 300                 self._handle_long_word(chunks, cur_line, cur_len, width)
 301
 302             # If the last chunk on this line is all whitespace, drop it.
 303             if self.drop_whitespace and cur_line and cur_line[-1].strip() == '':
 304                 del cur_line[-1]
 305
 306             # Convert current line back to a string and store it in list
 307             # of all lines (return value).
 308             if cur_line:
 309                 lines.append(indent + ''.join(cur_line))
 310
 311         return lines
 312
 313
 314     # -- Public interface ----------------------------------------------
 315
 316     def wrap(self, text):
 317         """wrap(text : string) -> [string]
 318
 319         Reformat the single paragraph in 'text' so it fits in lines of
 320         no more than 'self.width' columns, and return a list of wrapped
 321         lines.  Tabs in 'text' are expanded with string.expandtabs(),
 322         and all other whitespace characters (including newline) are
 323         converted to space.
 324         """
 325         text = self._munge_whitespace(text)
 326         chunks = self._split(text)
 327         if self.fix_sentence_endings:
 328             self._fix_sentence_endings(chunks)
 329         return self._wrap_chunks(chunks)
 330
 331     def fill(self, text):
 332         """fill(text : string) -> string
 333
 334         Reformat the single paragraph in 'text' to fit in lines of no
 335         more than 'self.width' columns, and return a new string
 336         containing the entire wrapped paragraph.
 337         """
 338         return "\n".join(self.wrap(text))
 339
 340
 341 # -- Convenience interface ---------------------------------------------
 342
 343 def wrap(text, width=70, **kwargs):
 344     """Wrap a single paragraph of text, returning a list of wrapped lines.
 345
 346     Reformat the single paragraph in 'text' so it fits in lines of no
 347     more than 'width' columns, and return a list of wrapped lines.  By
 348     default, tabs in 'text' are expanded with string.expandtabs(), and
 349     all other whitespace characters (including newline) are converted to
 350     space.  See TextWrapper class for available keyword args to customize
 351     wrapping behaviour.
 352     """
 353     w = TextWrapper(width=width, **kwargs)
 354     return w.wrap(text)
 355
 356 def fill(text, width=70, **kwargs):
 357     """Fill a single paragraph of text, returning a new string.
 358
 359     Reformat the single paragraph in 'text' to fit in lines of no more
 360     than 'width' columns, and return a new string containing the entire
 361     wrapped paragraph.  As with wrap(), tabs are expanded and other
 362     whitespace characters converted to space.  See TextWrapper class for
 363     available keyword args to customize wrapping behaviour.
 364     """
 365     w = TextWrapper(width=width, **kwargs)
 366     return w.fill(text)
 367
 368
 369 # -- Loosely related functionality -------------------------------------
 370
 371 _whitespace_only_re = re.compile('^[ \t]+$', re.MULTILINE)
 372 _leading_whitespace_re = re.compile('(^[ \t]*)(?:[^ \t\n])', re.MULTILINE)
 373
 374 def dedent(text):
 375     """Remove any common leading whitespace from every line in `text`.
 376
 377     This can be used to make triple-quoted strings line up with the left
 378     edge of the display, while still presenting them in the source code
 379     in indented form.
 380
 381     Note that tabs and spaces are both treated as whitespace, but they
 382     are not equal: the lines "  hello" and "\\thello" are
 383     considered to have no common leading whitespace.  (This behaviour is
 384     new in Python 2.5; older versions of this module incorrectly
 385     expanded tabs before searching for common leading whitespace.)
 386     """
 387     # Look for the longest leading string of spaces and tabs common to
 388     # all lines.
 389     margin = None
 390     text = _whitespace_only_re.sub('', text)
 391     indents = _leading_whitespace_re.findall(text)
 392     for indent in indents:
 393         if margin is None:
 394             margin = indent
 395
 396         # Current line more deeply indented than previous winner:
 397         # no change (previous winner is still on top).
 398         elif indent.startswith(margin):
 399             pass
 400
 401         # Current line consistent with and no deeper than previous winner:
 402         # it's the new winner.
 403         elif margin.startswith(indent):
 404             margin = indent
 405
 406         # Current line and previous winner have no common whitespace:
 407         # there is no margin.
 408         else:
 409             margin = ""
 410             break
 411
 412     # sanity check (testing/debugging only)
 413     if 0 and margin:
 414         for line in text.split("\n"):
 415             assert not line or line.startswith(margin), \
 416                    "line = %r, margin = %r" % (line, margin)
 417
 418     if margin:
 419         text = re.sub(r'(?m)^' + margin, '', text)
 420     return text
 421
 422 if __name__ == "__main__":
 423     #print dedent("\tfoo\n\tbar")
 424     #print dedent("  \thello there\n  \t  how are you?")
 425     print dedent("Hello there.\n  This is indented.")