如何找到一个目录下所有.txt文件

import os
root = "H:\ab123"
def findtxt(path, ret):
 """Finding the *.txt file in specify path"""
 filelist = os.listdir(path)
 for filename in filelist:
 de_path = os.path.join(path, filename)
 if os.path.isfile(de_path):
 if de_path.endswith(".txt"): #Specify to find the txt file.
 ret.append(de_path)
 else:
 findtxt(de_path, ret)
 
ret = []
findtxt(root, ret)
for path in ret:
 print(path)