编写程序，保存为demo6.py，运行后生成文件demo6

编写程序，保存为demo6.py，运行后生成文件demo6_new.py，其中的内容与demo6.py一致，但是在每行的行尾加上了行号。

filename = 'demo6.py'
with open(filename, 'r') as fp:
    lines = fp.readlines()
maxLength = len(max(lines, key=len))
lines = [line.rstrip().ljust(maxLength)+'#'+str(index)+'n'
         for index, line in enumerate(lines)]
with open(filename[:-3]+'_new.py', 'w') as fp:
    fp.writelines(lines)