我如何在Python中指明字符串中的换行符,以便我可以将多行写入文本文件?


当前回答

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!

其他回答

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!

这取决于你想要多正确。\n通常会做这项工作。如果你真的想要正确,你可以在os包中查找换行符。(这实际上叫做linesep。)

注意:当使用Python API写入文件时,不要使用os.linesep。只使用\n;Python会自动将其转换为适合您平台的换行符。

简单的解决方案

如果只调用print而不带任何参数,它将输出一个空行。

print

你可以像这样将输出管道到一个文件中(考虑到你的例子):

f = open('out.txt', 'w')
print 'First line' >> f
print >> f
print 'Second line' >> f
f.close()

它不仅与操作系统无关(甚至不需要使用操作系统包),而且比将\n放在字符串中更具可读性。

解释

print()函数有一个可选的关键字参数,用于字符串的结尾,称为end,默认为操作系统的换行符,例如。\ n。所以,当你调用print('hello')时,Python实际上打印的是'hello' + '\n'。这意味着当你只调用print而不带任何参数时,它实际上打印的是" + '\n',结果是换行符。

替代

使用多行字符串。

s = """First line
    Second line
    Third line"""
f = open('out.txt', 'w')
print s >> f
f.close()

您可以单独写入新行,也可以在单个字符串中写入,这样更容易。

示例1

输入

line1 = "hello how are you"
line2 = "I am testing the new line escape sequence"
line3 = "this seems to work"

你可以把“\n”分开写:

file.write(line1)
file.write("\n")
file.write(line2)
file.write("\n")
file.write(line3)
file.write("\n")

输出

hello how are you
I am testing the new line escape sequence
this seems to work

示例2

输入

正如其他人在之前的回答中指出的那样,将\n放在字符串中的相关点:

line = "hello how are you\nI am testing the new line escape sequence\nthis seems to work"

file.write(line)

输出

hello how are you
I am testing the new line escape sequence
this seems to work

各种等效方法

使用打印

默认情况下,打印已经追加了换行符!

with open("out.txt", "w") as f:
    print("First", file=f)
    print("Second", file=f)

等同于:

with open("out.txt", "w") as f:
    print("First\nSecond", file=f)

要打印而不自动添加换行符,使用sep=""(因为sep="\n"是默认值):

with open("out.txt", "w") as f:
    print("First\nSecond\n", sep="", file=f)

使用f.write

对于以文本模式打开的文件:

with open("out.txt", "w") as f:
    f.write("First\nSecond\n")

对于以二进制模式打开的文件,写入文件时不会自动将\n转换为特定于平台的行结束符。要强制使用当前平台的换行符,请使用os。Linesep代替\n:

with open("out.txt", "wb") as f:
    f.write("First" + os.linesep)
    f.write("Second" + os.linesep)

输出文件

视觉:

First
Second

在Linux上,换行符将以\n分隔:

First\nSecond\n

在Windows中,换行符将以\r\n分隔:

First\r\nSecond\r\n

为了避免以文本模式打开的文件自动将\n转换为\r\n,请使用open("out.txt", "w", newline="\n")打开文件。