def modify_content(file, old, new):
    """替换文件中的指定内容，逐行进行"""
    try:
        lines = open(file, 'r').readlines()
        f_len = len(lines) - 1
        for i in range(f_len):
            if old in lines[i]:
                lines[i] = lines[i].replace(old, new)
        open(file, 'w').writelines(lines)
    except Exception as e:
        print(e)