python textwrap_python textwrap -格式化文本段落
textwrap模块可用于格式化文本，以便在需要漂亮打印的情况下输出。它提供的编程功能类似于许多文本编辑器和文字处理器中的段落换行或填充功能。
示例数据
本节中的示例使用textwrap_example.py包含字符串的模块sample_text。
textwrap_example.py
sample_text = '''
The textwrap module can be used to format text for output in
situations where pretty-printing is desired. It offers
programmatic functionality similar to the paragraph wrapping
or filling features found in many text editors.
'''
灌装段落
该fill()函数将文本作为输入，并生成格式化的文本作为输出。
textwrap_fill.py
import textwrap
from textwrap_example import sample_text
print(textwrap.fill(sample_text, width=50))
结果差强人意。现在，文本左对齐，但是第一行保留缩进，并且每行后面的空格都嵌入到段落中。
$ python3 textwrap_fill.py
The textwrap module can be used to format
text for output in situations where pretty-
printing is desired. It offers programmatic
functionality similar to the paragraph wrapping
or filling features found in many text editors.
删除现有的缩进
前面的示例在输出的中间有嵌入的制表符和多余的空格，因此其格式不是很干净。从示例文本的所有行中删除公共空格前缀dedent()会产生更好的结果，并允许直接从Python代码使用docstrings或嵌入的多行字符串，同时删除代码本身的格式。示例字符串具有人工缩进级别，用于说明此功能。
textwrap_dedent.py
import textwrap
from textwrap_example import sample_text
dedented_text = textwrap.dedent(sample_text)
print('Dedented:')
print(dedented_text)
结果开始看起来更好。
$ python3 textwrap_dedent.py
Dedented:
The textwrap module can be used to format text for output in
situations where pretty-printing is desired. It offers
programmatic functionality similar to the paragraph wrapping
or filling features found in many text editors.
由于“缩进”与“缩进”相反，因此结果是一块文本，其中每行都删除了公共的初始空白。如果一行的缩进量已超过另一行，则某些空白将不会被删除。
输入像
␣Line one.
␣␣␣Line two.
␣Line three.
变成
Line one.
␣␣Line two.
Line three.
结合迪登并填写
接下来，可以fill()使用几个不同的width值传递下划线的文本。
textwrap_fill_width.py
import textwrap
from textwrap_example import sample_text
dedented_text = textwrap.dedent(sample_text).strip()
for width in [45, 60]:
print('{} Columns:\n'.format(width))
print(textwrap.fill(dedented_text, width=width))
print()
这将产生指定宽度的输出。
$ python3 textwrap_fill_width.py
45 Columns:
The textwrap module can be used to format
text for output in situations where pretty-
printing is desired. It offers programmatic
functionality similar to the paragraph
wrapping or filling features found in many
text editors.
60 Columns:
The textwrap module can be used to format text for output in
situations where pretty-printing is desired. It offers
programmatic functionality similar to the paragraph wrapping
or filling features found in many text editors.
缩进块
使用此indent()功能可将一致的前缀文本添加到字符串中的所有行。此示例的格式与示例文本相同，就好像它是答复中引用的电子邮件的一部分>一样，用作每行的前缀。
textwrap_indent.py
import textwrap
from textwrap_example import sample_text
dedented_text = textwrap.dedent(sample_text)
wrapped = textwrap.fill(dedented_text, width=50)
wrapped += '\n\nSecond paragraph after a blank line.'
final = textwrap.indent(wrapped, '> ')
print('Quoted block:\n')
print(final)
文本块在换行符上分割，将前缀添加到包含文本的每行中，然后将这些行组合回一个新字符串并返回。
$ python3 textwrap_indent.py
Quoted block:
The textwrap module can be used to format text
for output in situations where pretty-printing is
desired. It offers programmatic functionality
similar to the paragraph wrapping or filling
features found in many text editors.
Second paragraph after a blank line.
要控制哪些行接收新的前缀，请将callable作为predicate参数传递 给indent()。将依次为每一行文本调用callable，并为返回值为true的行添加前缀。
textwrap_indent_predicate.py
import textwrap
from textwrap_example import sample_text
def should_indent(line):
print('Indent {!r}?'.format(line))
return len(line.strip()) % 2 == 0
dedented_text = textwrap.dedent(sample_text)
wrapped = textwrap.fill(dedented_text, width=50)
final = textwrap.indent(wrapped, 'EVEN ',
predicate=should_indent)
print('\nQuoted block:\n')
print(final)
本示例将前缀添加EVEN到包含偶数个字符的行。
$ python3 textwrap_indent_predicate.py
Indent ' The textwrap module can be used to format text\n'?
Indent 'for output in situations where pretty-printing is\n'?
Indent 'desired. It offers programmatic functionality\n'?
Indent 'similar to the paragraph wrapping or filling\n'?
Indent 'features found in many text editors.'?
Quoted block:
EVEN The textwrap module can be used to format text
for output in situations where pretty-printing is
EVEN desired. It offers programmatic functionality
EVEN similar to the paragraph wrapping or filling
EVEN features found in many text editors.
悬挂缩进
以可能设置输出宽度的相同方式，可以独立于后续行来控制第一行的缩进。
textwrap_hanging_indent.py
import textwrap
from textwrap_example import sample_text
dedented_text = textwrap.dedent(sample_text).strip()
print(textwrap.fill(dedented_text,
initial_indent='',
subsequent_indent=' ' * 4,
width=50,
))
这使得可以产生悬挂的凹痕，其中第一行的凹痕小于其他行。
$ python3 textwrap_hanging_indent.py
The textwrap module can be used to format text for
output in situations where pretty-printing is
desired. It offers programmatic functionality
similar to the paragraph wrapping or filling
features found in many text editors.
缩进值也可以包含非空格字符。例如，悬挂的缩进可以带有前缀*以产生项目符号点。
截断长文本
要截断文本以创建摘要或预览，请使用 shorten()。所有现有的空白，例如制表符，换行符和一系列的多个空格，都将被标准化为一个空格。然后，在单词边界之间，文本将被截断为小于或等于所请求长度的长度，以便不包括部分单词。
textwrap_shorten.py
import textwrap
from textwrap_example import sample_text
dedented_text = textwrap.dedent(sample_text)
original = textwrap.fill(dedented_text, width=50)
print('Original:\n')
print(original)
shortened = textwrap.shorten(original, 100)
shortened_wrapped = textwrap.fill(shortened, width=50)
print('\nShortened:\n')
print(shortened_wrapped)
如果作为截断的一部分将非空白文本从原始文本中删除，则将其替换为占位符值。[...]可以通过提供placeholder 参数来替换默认值shorten()。
$ python3 textwrap_shorten.py
Original:
The textwrap module can be used to format text
for output in situations where pretty-printing is
desired. It offers programmatic functionality
similar to the paragraph wrapping or filling
features found in many text editors.
Shortened:
The textwrap module can be used to format text for
output in situations where pretty-printing [...]