编写一个读取大文件txt内容，然后按行替换特定字符串并写入原文件的pyhton脚本

我可以提供一些帮助。下面是Python脚本的示例：with open('filename.txt', 'r') as f:
lines = f.readlines()with open('filename.txt', 'w') as f_out:
for line in lines:
line = line.replace('old string', 'new string')
f_out.write(line)