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 = os.path.getsize(fullpath)
            res[fullpath] = size/1024/1024
    return sorted(res.items(), key = lambda d:d[1], reverse = True)

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