如何用Python移除文本文件中的^M(Control M)字符并保持行连续

问题描述 #

我的原始文件内容如下：

This line has control character ^M this is bad
I will try it

我想用Python移除文件中的Control M字符（即\r），生成的目标文件内容应该是：

This line has control character  this is bad
I will try it

我尝试了两种替换方式：

• line.replace("\r", "")
• line.replace("\r\n", "")

使用的代码片段如下：

with open(file_path, "r") as input_file:
    lines = input_file.readlines()

new_lines = []
for line in lines:
    new_line = line.replace("\r", "")
    new_lines.append(new_line)

new_file_name = "replace_control_char.dat"
new_file_path = os.path.join(here, data_dir, new_file_name)
with open(new_file_path, "w") as output_file:
    for line in new_lines:
        output_file.write(line)

但生成的新文件结果却变成了这样：

This line has control character
 this is bad
I will try it

原本同一行的内容被拆成了两行，我需要移除Control M后仍保持内容在同一行，求解决办法。

原因分析 #

问题出在readlines()的默认处理逻辑上——Python用文本模式读文件时，会把\r、\n、\r\n都当成换行符，所以原本带\r的单行内容被拆成了两行读进来。之后替换掉\r，但已经拆好的两行没法自动合并，就出现了现在的问题。

解决方法 #

方法一：二进制模式读写 #

直接用二进制模式读取整个文件，替换掉\r对应的字节后再写入，完全保留原始行结构：

import os

with open(file_path, "rb") as input_file:
    content = input_file.read()

# 替换\r字节为空字节
new_content = content.replace(b"\r", b"")

new_file_name = "replace_control_char.dat"
new_file_path = os.path.join(here, data_dir, new_file_name)
with open(new_file_path, "wb") as output_file:
    output_file.write(new_content)

方法二：指定newline=''读取 #

在文本模式下打开文件时加上newline=''参数，Python就不会自动转换行结束符，能完整读取原始行内容，再替换掉行内的\r即可：

import os

with open(file_path, "r", newline='') as input_file:
    lines = input_file.readlines()

new_lines = []
for line in lines:
    # 替换行内的\r字符
    new_line = line.replace("\r", "")
    new_lines.append(new_line)

new_file_name = "replace_control_char.dat"
new_file_path = os.path.join(here, data_dir, new_file_name)
with open(new_file_path, "w") as output_file:
    for line in new_lines:
        output_file.write(line)

这两种方法都能确保移除Control M字符后，原本的单行内容不会被拆分。

内容的提问来源于stack exchange，提问作者Arthur