学的 os , os.path 模块对文件目录处理，顺便实战一下。

import os

def list_size(path):
    res={}
    for dirpath, dirnames, filenames in os.walk(path):
        for name in filenames:
            fullpath = os.path.join(dirpath, name)
            size = round(os.path.getsize(fullpath))
            if size>0:
                res[fullpath] = round(size/1024/1024)
    return sorted(res.items(), key = lambda d:d[1], reverse = True)

path = 'E:'
with open(os.path.join('E:', 'filesize.txt'),'w') as f:
    for i in list_size(path):
        f.write(i[0]+'\t'+str(i[1])+'MB'+'\n')

os.listdir 只能看当前目录的文件，子文件夹的就不管了，所以就需要 os.walk 的遍历了。虽然小，不过还是挺实用的程序。