textwrap
--- 文本包装与填充¶
源代码: Lib/textwrap.py
textwrap
模块提供了一些快捷函数,以及可以完成所有工作的类 TextWrapper
。 如果你只是要包装或填充一两个文本字符串,快捷函数应该就够用了;否则的话,你应该使用 TextWrapper
的实例来提高效率。
-
textwrap.
wrap
(text, width=70, **kwargs)¶ 包装 text (字符串) 中的单独段落以使每行长度最多为 width 个字符。 返回由输出行组成的列表,行尾不带换行符。
可选的关键字参数对应于
TextWrapper
的实例属性,具体文档见下。 width 默认为70
。请参阅
TextWrapper.wrap()
方法了解有关wrap()
行为的详细信息。
-
textwrap.
fill
(text, width=70, **kwargs)¶ 包装 text 中的单独段落,并返回一个包含被包装段落的单独字符串。
fill()
是以下语句的快捷方式"\n".join(wrap(text, ...))
-
textwrap.
shorten
(text, width, **kwargs)¶ 折叠并截短给定的 text 以符合给定的 width。
首先将折叠 text 中的空格(所有连续空格替换为单个空格)。 如果结果能适合 width 则将其返回。 否则将丢弃足够数量的末尾单词以使得剩余单词加
placeholder
能适合width
:>>> textwrap.shorten("Hello world!", width=12) 'Hello world!' >>> textwrap.shorten("Hello world!", width=11) 'Hello [...]' >>> textwrap.shorten("Hello world", width=10, placeholder="...") 'Hello...'
可选的关键字参数对应于
TextWrapper
的实际属性,具体见下文。 请注意文本在被传入TextWrapper
的fill()
函数之前会被折叠,因此改变tabsize
,expand_tabs
,drop_whitespace
和replace_whitespace
的值将没有任何效果。3.4 新版功能.
-
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.Lines containing only whitespace are ignored in the input and normalized to a single newline character in the output.
例如:
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).
例如:
>>> 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 新版功能.
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 examplewrapper = 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 thanwidth
,TextWrapper
guarantees that no output line will be longer thanwidth
characters.
-
expand_tabs
¶ (default:
True
) If true, then all tab characters in text will be expanded to spaces using theexpandtabs()
method of text.
-
tabsize
¶ (default:
8
) Ifexpand_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 新版功能.
-
replace_whitespace
¶ (default:
True
) If true, after tab expansion but before wrapping, thewrap()
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'
).注解
If
expand_tabs
is false andreplace_whitespace
is true, each tab character will be replaced by a single space, which is not the same as tab expansion.注解
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 (usingstr.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 thanwidth
will be broken in order to ensure that no lines are longer thanwidth
. If it is false, long words will not be broken, and some lines may be longer thanwidth
. (Long words will be put on a line by themselves, in order to minimize the amount by whichwidth
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 setbreak_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 notNone
, then the output will contain at most max_lines lines, with placeholder appearing at the end of the output.3.4 新版功能.
-
placeholder
¶ (default:
' [...]'
) String that will appear at the end of the output text if it has been truncated.3.4 新版功能.
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 theTextWrapper
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.
-