| """Text wrapping and filling. |
| """ |
| |
| # Copyright (C) 1999-2001 Gregory P. Ward. |
| # Copyright (C) 2002, 2003 Python Software Foundation. |
| # Written by Greg Ward <gward@python.net> |
| |
| __revision__ = "$Id$" |
| |
| import string, re |
| |
| # Do the right thing with boolean values for all known Python versions |
| # (so this module can be copied to projects that don't depend on Python |
| # 2.3, e.g. Optik and Docutils). |
| try: |
| True, False |
| except NameError: |
| (True, False) = (1, 0) |
| |
| __all__ = ['TextWrapper', 'wrap', 'fill'] |
| |
| # Hardcode the recognized whitespace characters to the US-ASCII |
| # whitespace characters. The main reason for doing this is that in |
| # ISO-8859-1, 0xa0 is non-breaking whitespace, so in certain locales |
| # that character winds up in string.whitespace. Respecting |
| # string.whitespace in those cases would 1) make textwrap treat 0xa0 the |
| # same as any other whitespace char, which is clearly wrong (it's a |
| # *non-breaking* space), 2) possibly cause problems with Unicode, |
| # since 0xa0 is not in range(128). |
| _whitespace = '\t\n\x0b\x0c\r ' |
| |
| class TextWrapper: |
| """ |
| Object for wrapping/filling text. The public interface consists of |
| the wrap() and fill() methods; the other methods are just there for |
| subclasses to override in order to tweak the default behaviour. |
| If you want to completely replace the main wrapping algorithm, |
| you'll probably have to override _wrap_chunks(). |
| |
| Several instance attributes control various aspects of wrapping: |
| width (default: 70) |
| the maximum width of wrapped lines (unless break_long_words |
| is false) |
| initial_indent (default: "") |
| string that will be prepended to the first line of wrapped |
| output. Counts towards the line's width. |
| subsequent_indent (default: "") |
| string that will be prepended to all lines save the first |
| of wrapped output; also counts towards each line's width. |
| expand_tabs (default: true) |
| Expand tabs in input text to spaces before further processing. |
| Each tab will become 1 .. 8 spaces, depending on its position in |
| its line. If false, each tab is treated as a single character. |
| replace_whitespace (default: true) |
| Replace all whitespace characters in the input text by spaces |
| after tab expansion. Note that if expand_tabs is false and |
| replace_whitespace is true, every tab will be converted to a |
| single space! |
| fix_sentence_endings (default: false) |
| Ensure that sentence-ending punctuation is always followed |
| by two spaces. Off by default because the algorithm is |
| (unavoidably) imperfect. |
| break_long_words (default: true) |
| Break words longer than 'width'. If false, those words will not |
| be broken, and some lines might be longer than 'width'. |
| """ |
| |
| whitespace_trans = string.maketrans(_whitespace, ' ' * len(_whitespace)) |
| |
| unicode_whitespace_trans = {} |
| uspace = ord(u' ') |
| for x in map(ord, _whitespace): |
| unicode_whitespace_trans[x] = uspace |
| |
| # This funky little regex is just the trick for splitting |
| # text up into word-wrappable chunks. E.g. |
| # "Hello there -- you goof-ball, use the -b option!" |
| # splits into |
| # Hello/ /there/ /--/ /you/ /goof-/ball,/ /use/ /the/ /-b/ /option! |
| # (after stripping out empty strings). |
| wordsep_re = re.compile(r'(\s+|' # any whitespace |
| r'[^\s\w]*\w{2,}-(?=\w{2,})|' # hyphenated words |
| r'(?<=[\w\!\"\'\&\.\,\?])-{2,}(?=\w))') # em-dash |
| |
| # XXX this is not locale- or charset-aware -- string.lowercase |
| # is US-ASCII only (and therefore English-only) |
| sentence_end_re = re.compile(r'[%s]' # lowercase letter |
| r'[\.\!\?]' # sentence-ending punct. |
| r'[\"\']?' # optional end-of-quote |
| % string.lowercase) |
| |
| |
| def __init__(self, |
| width=70, |
| initial_indent="", |
| subsequent_indent="", |
| expand_tabs=True, |
| replace_whitespace=True, |
| fix_sentence_endings=False, |
| break_long_words=True): |
| self.width = width |
| self.initial_indent = initial_indent |
| self.subsequent_indent = subsequent_indent |
| self.expand_tabs = expand_tabs |
| self.replace_whitespace = replace_whitespace |
| self.fix_sentence_endings = fix_sentence_endings |
| self.break_long_words = break_long_words |
| |
| |
| # -- Private methods ----------------------------------------------- |
| # (possibly useful for subclasses to override) |
| |
| def _munge_whitespace(self, text): |
| """_munge_whitespace(text : string) -> string |
| |
| Munge whitespace in text: expand tabs and convert all other |
| whitespace characters to spaces. Eg. " foo\tbar\n\nbaz" |
| becomes " foo bar baz". |
| """ |
| if self.expand_tabs: |
| text = text.expandtabs() |
| if self.replace_whitespace: |
| if isinstance(text, str): |
| text = text.translate(self.whitespace_trans) |
| elif isinstance(text, unicode): |
| text = text.translate(self.unicode_whitespace_trans) |
| return text |
| |
| |
| def _split(self, text): |
| """_split(text : string) -> [string] |
| |
| Split the text to wrap into indivisible chunks. Chunks are |
| not quite the same as words; see wrap_chunks() for full |
| details. As an example, the text |
| Look, goof-ball -- use the -b option! |
| breaks into the following chunks: |
| 'Look,', ' ', 'goof-', 'ball', ' ', '--', ' ', |
| 'use', ' ', 'the', ' ', '-b', ' ', 'option!' |
| """ |
| chunks = self.wordsep_re.split(text) |
| chunks = filter(None, chunks) |
| return chunks |
| |
| def _fix_sentence_endings(self, chunks): |
| """_fix_sentence_endings(chunks : [string]) |
| |
| Correct for sentence endings buried in 'chunks'. Eg. when the |
| original text contains "... foo.\nBar ...", munge_whitespace() |
| and split() will convert that to [..., "foo.", " ", "Bar", ...] |
| which has one too few spaces; this method simply changes the one |
| space to two. |
| """ |
| i = 0 |
| pat = self.sentence_end_re |
| while i < len(chunks)-1: |
| if chunks[i+1] == " " and pat.search(chunks[i]): |
| chunks[i+1] = " " |
| i += 2 |
| else: |
| i += 1 |
| |
| def _handle_long_word(self, chunks, cur_line, cur_len, width): |
| """_handle_long_word(chunks : [string], |
| cur_line : [string], |
| cur_len : int, width : int) |
| |
| Handle a chunk of text (most likely a word, not whitespace) that |
| is too long to fit in any line. |
| """ |
| space_left = max(width - cur_len, 1) |
| |
| # If we're allowed to break long words, then do so: put as much |
| # of the next chunk onto the current line as will fit. |
| if self.break_long_words: |
| cur_line.append(chunks[0][0:space_left]) |
| chunks[0] = chunks[0][space_left:] |
| |
| # Otherwise, we have to preserve the long word intact. Only add |
| # it to the current line if there's nothing already there -- |
| # that minimizes how much we violate the width constraint. |
| elif not cur_line: |
| cur_line.append(chunks.pop(0)) |
| |
| # If we're not allowed to break long words, and there's already |
| # text on the current line, do nothing. Next time through the |
| # main loop of _wrap_chunks(), we'll wind up here again, but |
| # cur_len will be zero, so the next line will be entirely |
| # devoted to the long word that we can't handle right now. |
| |
| def _wrap_chunks(self, chunks): |
| """_wrap_chunks(chunks : [string]) -> [string] |
| |
| Wrap a sequence of text chunks and return a list of lines of |
| length 'self.width' or less. (If 'break_long_words' is false, |
| some lines may be longer than this.) Chunks correspond roughly |
| to words and the whitespace between them: each chunk is |
| indivisible (modulo 'break_long_words'), but a line break can |
| come between any two chunks. Chunks should not have internal |
| whitespace; ie. a chunk is either all whitespace or a "word". |
| Whitespace chunks will be removed from the beginning and end of |
| lines, but apart from that whitespace is preserved. |
| """ |
| lines = [] |
| if self.width <= 0: |
| raise ValueError("invalid width %r (must be > 0)" % self.width) |
| |
| while chunks: |
| |
| # Start the list of chunks that will make up the current line. |
| # cur_len is just the length of all the chunks in cur_line. |
| cur_line = [] |
| cur_len = 0 |
| |
| # Figure out which static string will prefix this line. |
| if lines: |
| indent = self.subsequent_indent |
| else: |
| indent = self.initial_indent |
| |
| # Maximum width for this line. |
| width = self.width - len(indent) |
| |
| # First chunk on line is whitespace -- drop it, unless this |
| # is the very beginning of the text (ie. no lines started yet). |
| if chunks[0].strip() == '' and lines: |
| del chunks[0] |
| |
| while chunks: |
| l = len(chunks[0]) |
| |
| # Can at least squeeze this chunk onto the current line. |
| if cur_len + l <= width: |
| cur_line.append(chunks.pop(0)) |
| cur_len += l |
| |
| # Nope, this line is full. |
| else: |
| break |
| |
| # The current line is full, and the next chunk is too big to |
| # fit on *any* line (not just this one). |
| if chunks and len(chunks[0]) > width: |
| self._handle_long_word(chunks, cur_line, cur_len, width) |
| |
| # If the last chunk on this line is all whitespace, drop it. |
| if cur_line and cur_line[-1].strip() == '': |
| del cur_line[-1] |
| |
| # Convert current line back to a string and store it in list |
| # of all lines (return value). |
| if cur_line: |
| lines.append(indent + ''.join(cur_line)) |
| |
| return lines |
| |
| |
| # -- Public interface ---------------------------------------------- |
| |
| def wrap(self, text): |
| """wrap(text : string) -> [string] |
| |
| Reformat the single paragraph in 'text' so it fits in lines of |
| no more than 'self.width' columns, and return a list of wrapped |
| lines. Tabs in 'text' are expanded with string.expandtabs(), |
| and all other whitespace characters (including newline) are |
| converted to space. |
| """ |
| text = self._munge_whitespace(text) |
| indent = self.initial_indent |
| chunks = self._split(text) |
| if self.fix_sentence_endings: |
| self._fix_sentence_endings(chunks) |
| return self._wrap_chunks(chunks) |
| |
| def fill(self, text): |
| """fill(text : string) -> string |
| |
| Reformat the single paragraph in 'text' to fit in lines of no |
| more than 'self.width' columns, and return a new string |
| containing the entire wrapped paragraph. |
| """ |
| return "\n".join(self.wrap(text)) |
| |
| |
| # -- Convenience interface --------------------------------------------- |
| |
| def wrap(text, width=70, **kwargs): |
| """Wrap a single paragraph of text, returning a list of wrapped lines. |
| |
| Reformat the single paragraph in 'text' so it fits in lines of no |
| more than 'width' columns, and return a list of wrapped lines. By |
| default, tabs in 'text' are expanded with string.expandtabs(), and |
| all other whitespace characters (including newline) are converted to |
| space. See TextWrapper class for available keyword args to customize |
| wrapping behaviour. |
| """ |
| w = TextWrapper(width=width, **kwargs) |
| return w.wrap(text) |
| |
| def fill(text, width=70, **kwargs): |
| """Fill a single paragraph of text, returning a new string. |
| |
| Reformat the single paragraph in 'text' to fit in lines of no more |
| than 'width' columns, and return a new string containing the entire |
| wrapped paragraph. As with wrap(), tabs are expanded and other |
| whitespace characters converted to space. See TextWrapper class for |
| available keyword args to customize wrapping behaviour. |
| """ |
| w = TextWrapper(width=width, **kwargs) |
| return w.fill(text) |
| |
| |
| # -- Loosely related functionality ------------------------------------- |
| |
| def dedent(text): |
| """dedent(text : string) -> string |
| |
| Remove any whitespace than can be uniformly removed from the left |
| of every line in `text`. |
| |
| This can be used e.g. to make triple-quoted strings line up with |
| the left edge of screen/whatever, while still presenting it in the |
| source code in indented form. |
| |
| For example: |
| |
| def test(): |
| # end first line with \ to avoid the empty line! |
| s = '''\ |
| hello |
| world |
| ''' |
| print repr(s) # prints ' hello\n world\n ' |
| print repr(dedent(s)) # prints 'hello\n world\n' |
| """ |
| lines = text.expandtabs().split('\n') |
| margin = None |
| for line in lines: |
| content = line.lstrip() |
| if not content: |
| continue |
| indent = len(line) - len(content) |
| if margin is None: |
| margin = indent |
| else: |
| margin = min(margin, indent) |
| |
| if margin is not None and margin > 0: |
| for i in range(len(lines)): |
| lines[i] = lines[i][margin:] |
| |
| return '\n'.join(lines) |