300 lines
10 KiB
ReStructuredText
300 lines
10 KiB
ReStructuredText
: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>
|
|
|
|
**Source code:** :source:`Lib/textwrap.py`
|
|
|
|
--------------
|
|
|
|
The :mod:`textwrap` module provides some convenience functions,
|
|
as well as :class:`TextWrapper`, the class that does all the work.
|
|
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=70, **kwargs)
|
|
|
|
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``.
|
|
|
|
See the :meth:`TextWrapper.wrap` method for additional details on how
|
|
:func:`wrap` behaves.
|
|
|
|
|
|
.. function:: fill(text, width=70, **kwargs)
|
|
|
|
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`.
|
|
|
|
|
|
.. function:: shorten(text, width, **kwargs)
|
|
|
|
Collapse and truncate the given *text* to fit in the given *width*.
|
|
|
|
First the whitespace in *text* is collapsed (all whitespace is replaced by
|
|
single spaces). If the result fits in the *width*, it is returned.
|
|
Otherwise, enough words are dropped from the end so that the remaining words
|
|
plus the :attr:`placeholder` fit within :attr:`width`::
|
|
|
|
>>> textwrap.shorten("Hello world!", width=12)
|
|
'Hello world!'
|
|
>>> textwrap.shorten("Hello world!", width=11)
|
|
'Hello [...]'
|
|
>>> textwrap.shorten("Hello world", width=10, placeholder="...")
|
|
'Hello...'
|
|
|
|
Optional keyword arguments correspond to the instance attributes of
|
|
:class:`TextWrapper`, documented below. Note that the whitespace is
|
|
collapsed before the text is passed to the :class:`TextWrapper` :meth:`fill`
|
|
function, so changing the value of :attr:`.tabsize`, :attr:`.expand_tabs`,
|
|
:attr:`.drop_whitespace`, and :attr:`.replace_whitespace` will have no effect.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
.. 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.
|
|
|
|
Lines containing only whitespace are ignored in the input and normalized to a
|
|
single newline character in the output.
|
|
|
|
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'
|
|
|
|
|
|
.. function:: indent(text, prefix, predicate=None)
|
|
|
|
Add *prefix* to the beginning of selected lines in *text*.
|
|
|
|
Lines are separated by calling ``text.splitlines(True)``.
|
|
|
|
By default, *prefix* is added to all lines that do not consist
|
|
solely of whitespace (including any line endings).
|
|
|
|
For example::
|
|
|
|
>>> s = 'hello\n\n \nworld'
|
|
>>> indent(s, ' ')
|
|
' hello\n\n \n world'
|
|
|
|
The optional *predicate* argument can be used to control which lines
|
|
are indented. For example, it is easy to add *prefix* to even empty
|
|
and whitespace-only lines::
|
|
|
|
>>> print(indent(s, '+ ', lambda line: True))
|
|
+ hello
|
|
+
|
|
+
|
|
+ world
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
:func:`wrap`, :func:`fill` and :func:`shorten` work by creating a
|
|
:class:`TextWrapper` instance and calling a single method on it. That
|
|
instance is not reused, so for applications that process many text
|
|
strings using :func:`wrap` and/or :func:`fill`, it may be more efficient to
|
|
create your own :class:`TextWrapper` object.
|
|
|
|
Text is preferably wrapped on whitespaces and right after the hyphens in
|
|
hyphenated words; only then will long words be broken if necessary, unless
|
|
:attr:`TextWrapper.break_long_words` is set to false.
|
|
|
|
.. class:: TextWrapper(**kwargs)
|
|
|
|
The :class:`TextWrapper` constructor accepts a number of optional keyword
|
|
arguments. Each keyword argument corresponds to an 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:: 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:: 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:: tabsize
|
|
|
|
(default: ``8``) If :attr:`expand_tabs` is true, then all tab characters
|
|
in *text* will be expanded to zero or more spaces, depending on the
|
|
current column and the given tab size.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. attribute:: replace_whitespace
|
|
|
|
(default: ``True``) If true, after tab expansion but before wrapping,
|
|
the :meth:`wrap` method will replace each whitespace character
|
|
with a single space. The whitespace characters replaced are
|
|
as follows: tab, newline, vertical tab, formfeed, and carriage
|
|
return (``'\t\n\v\f\r'``).
|
|
|
|
.. 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.
|
|
|
|
.. note::
|
|
|
|
If :attr:`replace_whitespace` is false, newlines may appear in the
|
|
middle of a line and cause strange output. For this reason, text should
|
|
be split into paragraphs (using :meth:`str.splitlines` or similar)
|
|
which are wrapped separately.
|
|
|
|
|
|
.. attribute:: drop_whitespace
|
|
|
|
(default: ``True``) If true, whitespace at the beginning and ending of
|
|
every line (after wrapping but before indenting) is dropped.
|
|
Whitespace at the beginning of the paragraph, however, is not dropped
|
|
if non-whitespace follows it. If whitespace being dropped takes up an
|
|
entire line, the whole line is dropped.
|
|
|
|
|
|
.. attribute:: initial_indent
|
|
|
|
(default: ``''``) String that will be prepended to the first line of
|
|
wrapped output. Counts towards the length of the first line. The empty
|
|
string is not indented.
|
|
|
|
|
|
.. attribute:: 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:: 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:: 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.)
|
|
|
|
|
|
.. attribute:: break_on_hyphens
|
|
|
|
(default: ``True``) If true, wrapping will occur preferably on whitespaces
|
|
and right after hyphens in compound words, as it is customary in English.
|
|
If false, only whitespaces will be considered as potentially good places
|
|
for line breaks, but you need to set :attr:`break_long_words` to false if
|
|
you want truly insecable words. Default behaviour in previous versions
|
|
was to always allow breaking hyphenated words.
|
|
|
|
|
|
.. attribute:: max_lines
|
|
|
|
(default: ``None``) If not ``None``, then the output will contain at most
|
|
*max_lines* lines, with *placeholder* appearing at the end of the output.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
.. index:: single: ...; placeholder
|
|
|
|
.. attribute:: placeholder
|
|
|
|
(default: ``' [...]'``) String that will appear at the end of the output
|
|
text if it has been truncated.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
:class:`TextWrapper` also provides some public methods, analogous to the
|
|
module-level convenience functions:
|
|
|
|
.. method:: 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. If the wrapped output has no
|
|
content, the returned list is empty.
|
|
|
|
|
|
.. method:: fill(text)
|
|
|
|
Wraps the single paragraph in *text*, and returns a single string
|
|
containing the wrapped paragraph.
|