495 lines
19 KiB
Python
495 lines
19 KiB
Python
"""Text wrapping and filling.
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"""
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# Copyright (C) 1999-2001 Gregory P. Ward.
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# Copyright (C) 2002, 2003 Python Software Foundation.
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# Written by Greg Ward <gward@python.net>
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import re
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__all__ = ['TextWrapper', 'wrap', 'fill', 'dedent', 'indent', 'shorten']
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# Hardcode the recognized whitespace characters to the US-ASCII
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# whitespace characters. The main reason for doing this is that
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# some Unicode spaces (like \u00a0) are non-breaking whitespaces.
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_whitespace = '\t\n\x0b\x0c\r '
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class TextWrapper:
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"""
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Object for wrapping/filling text. The public interface consists of
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the wrap() and fill() methods; the other methods are just there for
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subclasses to override in order to tweak the default behaviour.
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If you want to completely replace the main wrapping algorithm,
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you'll probably have to override _wrap_chunks().
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Several instance attributes control various aspects of wrapping:
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width (default: 70)
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the maximum width of wrapped lines (unless break_long_words
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is false)
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initial_indent (default: "")
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string that will be prepended to the first line of wrapped
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output. Counts towards the line's width.
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subsequent_indent (default: "")
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string that will be prepended to all lines save the first
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of wrapped output; also counts towards each line's width.
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expand_tabs (default: true)
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Expand tabs in input text to spaces before further processing.
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Each tab will become 0 .. 'tabsize' spaces, depending on its position
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in its line. If false, each tab is treated as a single character.
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tabsize (default: 8)
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Expand tabs in input text to 0 .. 'tabsize' spaces, unless
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'expand_tabs' is false.
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replace_whitespace (default: true)
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Replace all whitespace characters in the input text by spaces
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after tab expansion. Note that if expand_tabs is false and
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replace_whitespace is true, every tab will be converted to a
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single space!
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fix_sentence_endings (default: false)
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Ensure that sentence-ending punctuation is always followed
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by two spaces. Off by default because the algorithm is
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(unavoidably) imperfect.
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break_long_words (default: true)
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Break words longer than 'width'. If false, those words will not
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be broken, and some lines might be longer than 'width'.
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break_on_hyphens (default: true)
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Allow breaking hyphenated words. If true, wrapping will occur
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preferably on whitespaces and right after hyphens part of
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compound words.
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drop_whitespace (default: true)
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Drop leading and trailing whitespace from lines.
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max_lines (default: None)
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Truncate wrapped lines.
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placeholder (default: ' [...]')
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Append to the last line of truncated text.
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"""
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unicode_whitespace_trans = {}
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uspace = ord(' ')
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for x in _whitespace:
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unicode_whitespace_trans[ord(x)] = uspace
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# This funky little regex is just the trick for splitting
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# text up into word-wrappable chunks. E.g.
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# "Hello there -- you goof-ball, use the -b option!"
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# splits into
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# Hello/ /there/ /--/ /you/ /goof-/ball,/ /use/ /the/ /-b/ /option!
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# (after stripping out empty strings).
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word_punct = r'[\w!"\'&.,?]'
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letter = r'[^\d\W]'
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whitespace = r'[%s]' % re.escape(_whitespace)
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nowhitespace = '[^' + whitespace[1:]
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wordsep_re = re.compile(r'''
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( # any whitespace
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%(ws)s+
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| # em-dash between words
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(?<=%(wp)s) -{2,} (?=\w)
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| # word, possibly hyphenated
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%(nws)s+? (?:
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# hyphenated word
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-(?: (?<=%(lt)s{2}-) | (?<=%(lt)s-%(lt)s-))
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(?= %(lt)s -? %(lt)s)
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| # end of word
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(?=%(ws)s|\Z)
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| # em-dash
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(?<=%(wp)s) (?=-{2,}\w)
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)
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)''' % {'wp': word_punct, 'lt': letter,
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'ws': whitespace, 'nws': nowhitespace},
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re.VERBOSE)
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del word_punct, letter, nowhitespace
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# This less funky little regex just split on recognized spaces. E.g.
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# "Hello there -- you goof-ball, use the -b option!"
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# splits into
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# Hello/ /there/ /--/ /you/ /goof-ball,/ /use/ /the/ /-b/ /option!/
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wordsep_simple_re = re.compile(r'(%s+)' % whitespace)
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del whitespace
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# XXX this is not locale- or charset-aware -- string.lowercase
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# is US-ASCII only (and therefore English-only)
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sentence_end_re = re.compile(r'[a-z]' # lowercase letter
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r'[\.\!\?]' # sentence-ending punct.
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r'[\"\']?' # optional end-of-quote
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r'\Z') # end of chunk
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def __init__(self,
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width=70,
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initial_indent="",
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subsequent_indent="",
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expand_tabs=True,
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replace_whitespace=True,
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fix_sentence_endings=False,
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break_long_words=True,
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drop_whitespace=True,
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break_on_hyphens=True,
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tabsize=8,
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*,
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max_lines=None,
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placeholder=' [...]'):
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self.width = width
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self.initial_indent = initial_indent
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self.subsequent_indent = subsequent_indent
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self.expand_tabs = expand_tabs
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self.replace_whitespace = replace_whitespace
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self.fix_sentence_endings = fix_sentence_endings
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self.break_long_words = break_long_words
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self.drop_whitespace = drop_whitespace
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self.break_on_hyphens = break_on_hyphens
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self.tabsize = tabsize
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self.max_lines = max_lines
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self.placeholder = placeholder
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# -- Private methods -----------------------------------------------
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# (possibly useful for subclasses to override)
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def _munge_whitespace(self, text):
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"""_munge_whitespace(text : string) -> string
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Munge whitespace in text: expand tabs and convert all other
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whitespace characters to spaces. Eg. " foo\\tbar\\n\\nbaz"
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becomes " foo bar baz".
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"""
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if self.expand_tabs:
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text = text.expandtabs(self.tabsize)
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if self.replace_whitespace:
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text = text.translate(self.unicode_whitespace_trans)
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return text
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def _split(self, text):
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"""_split(text : string) -> [string]
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Split the text to wrap into indivisible chunks. Chunks are
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not quite the same as words; see _wrap_chunks() for full
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details. As an example, the text
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Look, goof-ball -- use the -b option!
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breaks into the following chunks:
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'Look,', ' ', 'goof-', 'ball', ' ', '--', ' ',
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'use', ' ', 'the', ' ', '-b', ' ', 'option!'
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if break_on_hyphens is True, or in:
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'Look,', ' ', 'goof-ball', ' ', '--', ' ',
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'use', ' ', 'the', ' ', '-b', ' ', option!'
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otherwise.
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"""
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if self.break_on_hyphens is True:
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chunks = self.wordsep_re.split(text)
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else:
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chunks = self.wordsep_simple_re.split(text)
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chunks = [c for c in chunks if c]
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return chunks
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def _fix_sentence_endings(self, chunks):
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"""_fix_sentence_endings(chunks : [string])
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Correct for sentence endings buried in 'chunks'. Eg. when the
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original text contains "... foo.\\nBar ...", munge_whitespace()
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and split() will convert that to [..., "foo.", " ", "Bar", ...]
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which has one too few spaces; this method simply changes the one
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space to two.
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"""
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i = 0
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patsearch = self.sentence_end_re.search
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while i < len(chunks)-1:
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if chunks[i+1] == " " and patsearch(chunks[i]):
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chunks[i+1] = " "
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i += 2
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else:
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i += 1
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def _handle_long_word(self, reversed_chunks, cur_line, cur_len, width):
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"""_handle_long_word(chunks : [string],
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cur_line : [string],
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cur_len : int, width : int)
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Handle a chunk of text (most likely a word, not whitespace) that
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is too long to fit in any line.
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"""
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# Figure out when indent is larger than the specified width, and make
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# sure at least one character is stripped off on every pass
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if width < 1:
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space_left = 1
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else:
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space_left = width - cur_len
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# If we're allowed to break long words, then do so: put as much
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# of the next chunk onto the current line as will fit.
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if self.break_long_words:
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end = space_left
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chunk = reversed_chunks[-1]
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if self.break_on_hyphens and len(chunk) > space_left:
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# break after last hyphen, but only if there are
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# non-hyphens before it
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hyphen = chunk.rfind('-', 0, space_left)
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if hyphen > 0 and any(c != '-' for c in chunk[:hyphen]):
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end = hyphen + 1
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cur_line.append(chunk[:end])
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reversed_chunks[-1] = chunk[end:]
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# Otherwise, we have to preserve the long word intact. Only add
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# it to the current line if there's nothing already there --
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# that minimizes how much we violate the width constraint.
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elif not cur_line:
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cur_line.append(reversed_chunks.pop())
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# If we're not allowed to break long words, and there's already
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# text on the current line, do nothing. Next time through the
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# main loop of _wrap_chunks(), we'll wind up here again, but
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# cur_len will be zero, so the next line will be entirely
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# devoted to the long word that we can't handle right now.
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def _wrap_chunks(self, chunks):
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"""_wrap_chunks(chunks : [string]) -> [string]
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Wrap a sequence of text chunks and return a list of lines of
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length 'self.width' or less. (If 'break_long_words' is false,
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some lines may be longer than this.) Chunks correspond roughly
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to words and the whitespace between them: each chunk is
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indivisible (modulo 'break_long_words'), but a line break can
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come between any two chunks. Chunks should not have internal
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whitespace; ie. a chunk is either all whitespace or a "word".
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Whitespace chunks will be removed from the beginning and end of
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lines, but apart from that whitespace is preserved.
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"""
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lines = []
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if self.width <= 0:
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raise ValueError("invalid width %r (must be > 0)" % self.width)
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if self.max_lines is not None:
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if self.max_lines > 1:
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indent = self.subsequent_indent
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else:
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indent = self.initial_indent
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if len(indent) + len(self.placeholder.lstrip()) > self.width:
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raise ValueError("placeholder too large for max width")
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# Arrange in reverse order so items can be efficiently popped
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# from a stack of chucks.
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chunks.reverse()
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while chunks:
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# Start the list of chunks that will make up the current line.
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# cur_len is just the length of all the chunks in cur_line.
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cur_line = []
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cur_len = 0
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# Figure out which static string will prefix this line.
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if lines:
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indent = self.subsequent_indent
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else:
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indent = self.initial_indent
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# Maximum width for this line.
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width = self.width - len(indent)
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# First chunk on line is whitespace -- drop it, unless this
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# is the very beginning of the text (ie. no lines started yet).
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if self.drop_whitespace and chunks[-1].strip() == '' and lines:
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del chunks[-1]
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while chunks:
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l = len(chunks[-1])
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# Can at least squeeze this chunk onto the current line.
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if cur_len + l <= width:
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cur_line.append(chunks.pop())
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cur_len += l
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# Nope, this line is full.
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else:
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break
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# The current line is full, and the next chunk is too big to
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# fit on *any* line (not just this one).
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if chunks and len(chunks[-1]) > width:
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self._handle_long_word(chunks, cur_line, cur_len, width)
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cur_len = sum(map(len, cur_line))
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# If the last chunk on this line is all whitespace, drop it.
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if self.drop_whitespace and cur_line and cur_line[-1].strip() == '':
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cur_len -= len(cur_line[-1])
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del cur_line[-1]
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if cur_line:
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if (self.max_lines is None or
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len(lines) + 1 < self.max_lines or
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(not chunks or
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self.drop_whitespace and
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len(chunks) == 1 and
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not chunks[0].strip()) and cur_len <= width):
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# Convert current line back to a string and store it in
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# list of all lines (return value).
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lines.append(indent + ''.join(cur_line))
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else:
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while cur_line:
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if (cur_line[-1].strip() and
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cur_len + len(self.placeholder) <= width):
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cur_line.append(self.placeholder)
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lines.append(indent + ''.join(cur_line))
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break
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cur_len -= len(cur_line[-1])
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del cur_line[-1]
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else:
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if lines:
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prev_line = lines[-1].rstrip()
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if (len(prev_line) + len(self.placeholder) <=
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self.width):
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lines[-1] = prev_line + self.placeholder
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break
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lines.append(indent + self.placeholder.lstrip())
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break
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return lines
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def _split_chunks(self, text):
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text = self._munge_whitespace(text)
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return self._split(text)
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# -- Public interface ----------------------------------------------
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def wrap(self, text):
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"""wrap(text : string) -> [string]
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Reformat the single paragraph in 'text' so it fits in lines of
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no more than 'self.width' columns, and return a list of wrapped
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lines. Tabs in 'text' are expanded with string.expandtabs(),
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and all other whitespace characters (including newline) are
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converted to space.
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"""
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chunks = self._split_chunks(text)
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if self.fix_sentence_endings:
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self._fix_sentence_endings(chunks)
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return self._wrap_chunks(chunks)
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def fill(self, text):
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"""fill(text : string) -> string
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Reformat the single paragraph in 'text' to fit in lines of no
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more than 'self.width' columns, and return a new string
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containing the entire wrapped paragraph.
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"""
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return "\n".join(self.wrap(text))
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# -- Convenience interface ---------------------------------------------
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def wrap(text, width=70, **kwargs):
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"""Wrap a single paragraph of text, returning a list of wrapped lines.
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Reformat the single paragraph in 'text' so it fits in lines of no
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more than 'width' columns, and return a list of wrapped lines. By
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default, tabs in 'text' are expanded with string.expandtabs(), and
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all other whitespace characters (including newline) are converted to
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space. See TextWrapper class for available keyword args to customize
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wrapping behaviour.
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"""
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w = TextWrapper(width=width, **kwargs)
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return w.wrap(text)
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def fill(text, width=70, **kwargs):
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"""Fill a single paragraph of text, returning a new string.
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Reformat the single paragraph in 'text' to fit in lines of no more
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than 'width' columns, and return a new string containing the entire
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wrapped paragraph. As with wrap(), tabs are expanded and other
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whitespace characters converted to space. See TextWrapper class for
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available keyword args to customize wrapping behaviour.
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"""
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w = TextWrapper(width=width, **kwargs)
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return w.fill(text)
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def shorten(text, width, **kwargs):
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"""Collapse and truncate the given text to fit in the given width.
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The text first has its whitespace collapsed. If it then fits in
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the *width*, it is returned as is. Otherwise, as many words
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as possible are joined and then the placeholder is appended::
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>>> textwrap.shorten("Hello world!", width=12)
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'Hello world!'
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>>> textwrap.shorten("Hello world!", width=11)
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'Hello [...]'
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"""
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w = TextWrapper(width=width, max_lines=1, **kwargs)
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return w.fill(' '.join(text.strip().split()))
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# -- Loosely related functionality -------------------------------------
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_whitespace_only_re = re.compile('^[ \t]+$', re.MULTILINE)
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_leading_whitespace_re = re.compile('(^[ \t]*)(?:[^ \t\n])', re.MULTILINE)
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def dedent(text):
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"""Remove any common leading whitespace from every line in `text`.
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This can be used to make triple-quoted strings line up with the left
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edge of the display, while still presenting them in the source code
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in indented form.
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Note that tabs and spaces are both treated as whitespace, but they
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are not equal: the lines " hello" and "\\thello" are
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considered to have no common leading whitespace.
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Entirely blank lines are normalized to a newline character.
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"""
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# Look for the longest leading string of spaces and tabs common to
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# all lines.
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margin = None
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text = _whitespace_only_re.sub('', text)
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indents = _leading_whitespace_re.findall(text)
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for indent in indents:
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if margin is None:
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margin = indent
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# Current line more deeply indented than previous winner:
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# no change (previous winner is still on top).
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elif indent.startswith(margin):
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pass
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# Current line consistent with and no deeper than previous winner:
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# it's the new winner.
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elif margin.startswith(indent):
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margin = indent
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# Find the largest common whitespace between current line and previous
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# winner.
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else:
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for i, (x, y) in enumerate(zip(margin, indent)):
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if x != y:
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margin = margin[:i]
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break
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# sanity check (testing/debugging only)
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if 0 and margin:
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for line in text.split("\n"):
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assert not line or line.startswith(margin), \
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"line = %r, margin = %r" % (line, margin)
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if margin:
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text = re.sub(r'(?m)^' + margin, '', text)
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return text
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def indent(text, prefix, predicate=None):
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"""Adds 'prefix' to the beginning of selected lines in 'text'.
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If 'predicate' is provided, 'prefix' will only be added to the lines
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where 'predicate(line)' is True. If 'predicate' is not provided,
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it will default to adding 'prefix' to all non-empty lines that do not
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consist solely of whitespace characters.
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"""
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if predicate is None:
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def predicate(line):
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return line.strip()
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def prefixed_lines():
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for line in text.splitlines(True):
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yield (prefix + line if predicate(line) else line)
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return ''.join(prefixed_lines())
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if __name__ == "__main__":
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#print dedent("\tfoo\n\tbar")
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#print dedent(" \thello there\n \t how are you?")
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print(dedent("Hello there.\n This is indented."))
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