在Python 3中，该语言会在平台的原生表示中为你编码换行符。这意味着在Windows上是\r\n，而在成熟的系统上只是\n。

即使在U*x系统上，以文本模式读取Windows行结束符的文件也会返回正确的文本结果，即在\n字符之前的任何\r字符都会被无声地删除。

如果需要完全控制文件中的字节，则可以使用二进制模式。然后，每个字节恰好对应一个字节，Python不执行任何转换。

>>> # Write a file with different line endings, using binary mode for full control
>>> with open('/tmp/demo.txt', 'wb') as wf:
...     wf.write(b'DOS line\r\n')
...     wf.write(b'U*x line\n')
...     wf.write(b'no line')
10
9
7

>>> # Read the file as text
>>> with open('/tmp/demo.txt', 'r') as text:
...     for line in text:
...         print(line, end='')
DOS line
U*x line
no line

>>> # Or more demonstrably
>>> with open('/tmp/demo.txt', 'r') as text:
...     for line in text:
...         print(repr(line))
'DOS line\n'
'U*x line\n'
'no line'

>>> # Back to bytes!
>>> with open('/tmp/demo.txt', 'rb') as binary:
...     for line in binary:
...         print(line)
b'DOS line\r\n'
b'U*x line\n'
b'no line'

>>> # Open in binary, but convert back to text
>>> with open('/tmp/demo.txt', 'rb') as binary:
...     for line in binary:
...         print(line.decode('utf-8'), end='')
DOS line
U*x line
no line

>>> # Or again in more detail, with repr()
>>> with open('/tmp/demo.txt', 'rb') as binary:
...     for line in binary:
...         print(repr(line.decode('utf-8')))
'DOS line\r\n'
'U*x line\n'
'no line'

'\n'也是一样，不过你可能不需要'\r'。在Java版本中使用它的原因是什么?如果你确实需要/想要它，你也可以在Python中以同样的方式使用它。

在Python中，你可以只使用换行符，即\n

正如在其他回答中提到的:“新的行字符是\n。它在字符串中使用”。

我发现最简单易读的方法是使用“format”函数，使用nl作为新行名称，并将你想打印的字符串转换为你要打印的确切格式:

Python 2:

print("line1{nl}"
      "line2{nl}"
      "line3".format(nl="\n"))

Python 3:

nl = "\n"
print(f"line1{nl}"
      f"line2{nl}"
      f"line3")

这将输出:

line1
line2
line3

通过这种方式，它可以执行任务，并且还提供了代码的高可读性:)

值得注意的是，当你使用交互式Python shell或Jupyter Notebook检查字符串时，\n和其他反划字符串(如\t)会逐字呈现:

>>> gotcha = 'Here is some random message...'
>>> gotcha += '\nAdditional content:\n\t{}'.format('Yet even more great stuff!')
>>> gotcha
'Here is some random message...\nAdditional content:\n\tYet even more great stuff!'

换行符、制表符和其他特殊的非打印字符只有在打印或写入文件时才会呈现为空白:

>>> print('{}'.format(gotcha))
Here is some random message...
Additional content:
    Yet even more great stuff!

这里有一个更易读的解决方案，即使你不在顶级缩进(例如，在函数定义中)，它也能正确工作。

import textwrap
file.write(textwrap.dedent("""
    Life's but a walking shadow, a poor player
    That struts and frets his hour upon the stage
    And then is heard no more: it is a tale
    Told by an idiot, full of sound and fury,
    Signifying nothing.
"""))