"textwrap" --- Text wrapping and filling
****************************************

**Source code:** Lib/textwrap.py

======================================================================

The "textwrap" module provides some convenience functions, as well as
"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
"TextWrapper" for efficiency.

textwrap.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
   "TextWrapper", documented below.  *width* defaults to "70".

   See the "TextWrapper.wrap()" method for additional details on how
   "wrap()" behaves.

textwrap.fill(text, width=70, **kwargs)

   Wraps the single paragraph in *text*, and returns a single string
   containing the wrapped paragraph.  "fill()" is shorthand for

      "\n".join(wrap(text, ...))

   In particular, "fill()" accepts exactly the same keyword arguments
   as "wrap()".

textwrap.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 "placeholder" fit within "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
   "TextWrapper", documented below.  Note that the whitespace is
   collapsed before the text is passed to the "TextWrapper" "fill()"
   function, so changing the value of "tabsize", "expand_tabs",
   "drop_whitespace", and "replace_whitespace" will have no effect.

   3.4 版新加入.

textwrap.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.

   只包含空白符的行会在输入时被忽略并在输出时被标准化为单个换行符。

   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'

textwrap.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

   3.3 版新加入.

"wrap()", "fill()" and "shorten()" work by creating a "TextWrapper"
instance and calling a single method on it.  That instance is not
reused, so for applications that process many text strings using
"wrap()" and/or "fill()", it may be more efficient to create your own
"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 "TextWrapper.break_long_words" is set to false.

class textwrap.TextWrapper(**kwargs)

   The "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 "TextWrapper" object many times, and you
   can change any of its options through direct assignment to instance
   attributes between uses.

   The "TextWrapper" instance attributes (and keyword arguments to the
   constructor) are as follows:

   width

      (default: "70") The maximum length of wrapped lines.  As long as
      there are no individual words in the input text longer than
      "width", "TextWrapper" guarantees that no output line will be
      longer than "width" characters.

   expand_tabs

      (default: "True") If true, then all tab characters in *text*
      will be expanded to spaces using the "expandtabs()" method of
      *text*.

   tabsize

      (default: "8") If "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.

      3.3 版新加入.

   replace_whitespace

      (default: "True") If true, after tab expansion but before
      wrapping, the "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'").

      備註: If "expand_tabs" is false and "replace_whitespace" is
        true, each tab character will be replaced by a single space,
        which is *not* the same as tab expansion.

      備註: If "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
        "str.splitlines()" or similar) which are wrapped separately.

   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.

   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.

   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.

   fix_sentence_endings

      (default: "False") If true, "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 [...]

      "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.

   break_long_words

      (default: "True") If true, then words longer than "width" will
      be broken in order to ensure that no lines are longer than
      "width".  If it is false, long words will not be broken, and
      some lines may be longer than "width".  (Long words will be put
      on a line by themselves, in order to minimize the amount by
      which "width" is exceeded.)

   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 "break_long_words" to false if you want truly
      insecable words.  Default behaviour in previous versions was to
      always allow breaking hyphenated words.

   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.

      3.4 版新加入.

   placeholder

      (default: "' [...]'") String that will appear at the end of the
      output text if it has been truncated.

      3.4 版新加入.

   "TextWrapper" also provides some public methods, analogous to the
   module-level convenience functions:

   wrap(text)

      Wraps the single paragraph in *text* (a string) so every line is
      at most "width" characters long.  All wrapping options are taken
      from instance attributes of the "TextWrapper" instance.  Returns
      a list of output lines, without final newlines.  If the wrapped
      output has no content, the returned list is empty.

   fill(text)

      Wraps the single paragraph in *text*, and returns a single
      string containing the wrapped paragraph.
