场景是在upordown.txt里找含某编号的行并替换内容找不到就把新内容追加到文件末尾。defmodify_line(number,new_content):path./logs/upordown.txtwithopen(path,r,encodingutf-8)asf:linesf.readlines()targetstr(number)foundFalsefori,lineinenumerate(lines):iftargetinline:newline\nifline.endswith(\n)elseifnew_content:lines[i]else:lines[i]new_contentnewline foundTrue# 没找到就追加到末尾ifnotfound:# 如果最后一行没有换行符先补一个iflinesandnotlines[-1].endswith(\n):lines[-1]\nlines.append(new_content\n)withopen(path,w,encodingutf-8)asf:f.writelines(lines)