import os
import os.path
def getListFiles(path):
    ret = []
    for root, dirs, files in os.walk(path):
        for filespath in files:
          ret.append(os.path.join(root,filespath))
    return ret
ret = getListFiles("E:\\")
# print(ret)
list = set()
for i in ret:
 # os.path.splitext():分離檔名與副檔名
      if os.path.splitext(i)[1]=='.txt':
            list.add(i)
print(list)