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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
commit | 116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch) | |
tree | 8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/textwrap.rst | |
parent | 739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff) | |
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Move the 3k reST doc tree in place.
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diff --git a/Doc/library/textwrap.rst b/Doc/library/textwrap.rst new file mode 100644 index 0000000..f729a64 --- /dev/null +++ b/Doc/library/textwrap.rst @@ -0,0 +1,192 @@ + +:mod:`textwrap` --- Text wrapping and filling +============================================= + +.. module:: textwrap + :synopsis: Text wrapping and filling +.. moduleauthor:: Greg Ward <gward@python.net> +.. sectionauthor:: Greg Ward <gward@python.net> + + +.. versionadded:: 2.3 + +The :mod:`textwrap` module provides two convenience functions, :func:`wrap` and +:func:`fill`, as well as :class:`TextWrapper`, the class that does all the work, +and a utility function :func:`dedent`. If you're just wrapping or filling one +or two text strings, the convenience functions should be good enough; +otherwise, you should use an instance of :class:`TextWrapper` for efficiency. + + +.. function:: wrap(text[, width[, ...]]) + + Wraps the single paragraph in *text* (a string) so every line is at most *width* + characters long. Returns a list of output lines, without final newlines. + + Optional keyword arguments correspond to the instance attributes of + :class:`TextWrapper`, documented below. *width* defaults to ``70``. + + +.. function:: fill(text[, width[, ...]]) + + Wraps the single paragraph in *text*, and returns a single string containing the + wrapped paragraph. :func:`fill` is shorthand for :: + + "\n".join(wrap(text, ...)) + + In particular, :func:`fill` accepts exactly the same keyword arguments as + :func:`wrap`. + +Both :func:`wrap` and :func:`fill` work by creating a :class:`TextWrapper` +instance and calling a single method on it. That instance is not reused, so for +applications that wrap/fill many text strings, it will be more efficient for you +to create your own :class:`TextWrapper` object. + +An additional utility function, :func:`dedent`, is provided to remove +indentation from strings that have unwanted whitespace to the left of the text. + + +.. function:: dedent(text) + + Remove any common leading whitespace from every line in *text*. + + This can be used to make triple-quoted strings line up with the left edge of the + display, while still presenting them in the source code in indented form. + + Note that tabs and spaces are both treated as whitespace, but they are not + equal: the lines ``" hello"`` and ``"\thello"`` are considered to have no + common leading whitespace. (This behaviour is new in Python 2.5; older versions + of this module incorrectly expanded tabs before searching for common leading + whitespace.) + + 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' + + +.. class:: TextWrapper(...) + + The :class:`TextWrapper` constructor accepts a number of optional keyword + arguments. Each argument corresponds to one instance attribute, so for example + :: + + wrapper = TextWrapper(initial_indent="* ") + + is the same as :: + + wrapper = TextWrapper() + wrapper.initial_indent = "* " + + You can re-use the same :class:`TextWrapper` object many times, and you can + change any of its options through direct assignment to instance attributes + between uses. + +The :class:`TextWrapper` instance attributes (and keyword arguments to the +constructor) are as follows: + + +.. attribute:: TextWrapper.width + + (default: ``70``) The maximum length of wrapped lines. As long as there are no + individual words in the input text longer than :attr:`width`, + :class:`TextWrapper` guarantees that no output line will be longer than + :attr:`width` characters. + + +.. attribute:: TextWrapper.expand_tabs + + (default: ``True``) If true, then all tab characters in *text* will be expanded + to spaces using the :meth:`expandtabs` method of *text*. + + +.. attribute:: TextWrapper.replace_whitespace + + (default: ``True``) If true, each whitespace character (as defined by + ``string.whitespace``) remaining after tab expansion will be replaced by a + single space. + + .. note:: + + If :attr:`expand_tabs` is false and :attr:`replace_whitespace` is true, each tab + character will be replaced by a single space, which is *not* the same as tab + expansion. + + +.. attribute:: TextWrapper.drop_whitespace + + (default: ``True``) If true, whitespace that, after wrapping, happens to end up + at the beginning or end of a line is dropped (leading whitespace in the first + line is always preserved, though). + + .. versionadded:: 2.6 + Whitespace was always dropped in earlier versions. + + +.. attribute:: TextWrapper.initial_indent + + (default: ``''``) String that will be prepended to the first line of wrapped + output. Counts towards the length of the first line. + + +.. attribute:: TextWrapper.subsequent_indent + + (default: ``''``) String that will be prepended to all lines of wrapped output + except the first. Counts towards the length of each line except the first. + + +.. attribute:: TextWrapper.fix_sentence_endings + + (default: ``False``) If true, :class:`TextWrapper` attempts to detect sentence + endings and ensure that sentences are always separated by exactly two spaces. + This is generally desired for text in a monospaced font. However, the sentence + detection algorithm is imperfect: it assumes that a sentence ending consists of + a lowercase letter followed by one of ``'.'``, ``'!'``, or ``'?'``, possibly + followed by one of ``'"'`` or ``"'"``, followed by a space. One problem with + this is algorithm is that it is unable to detect the difference between "Dr." in + :: + + [...] Dr. Frankenstein's monster [...] + + and "Spot." in :: + + [...] See Spot. See Spot run [...] + + :attr:`fix_sentence_endings` is false by default. + + Since the sentence detection algorithm relies on ``string.lowercase`` for the + definition of "lowercase letter," and a convention of using two spaces after + a period to separate sentences on the same line, it is specific to + English-language texts. + + +.. attribute:: TextWrapper.break_long_words + + (default: ``True``) If true, then words longer than :attr:`width` will be broken + in order to ensure that no lines are longer than :attr:`width`. If it is false, + long words will not be broken, and some lines may be longer than :attr:`width`. + (Long words will be put on a line by themselves, in order to minimize the amount + by which :attr:`width` is exceeded.) + +:class:`TextWrapper` also provides two public methods, analogous to the +module-level convenience functions: + + +.. method:: TextWrapper.wrap(text) + + Wraps the single paragraph in *text* (a string) so every line is at most + :attr:`width` characters long. All wrapping options are taken from instance + attributes of the :class:`TextWrapper` instance. Returns a list of output lines, + without final newlines. + + +.. method:: TextWrapper.fill(text) + + Wraps the single paragraph in *text*, and returns a single string containing the + wrapped paragraph. + |