def _dir_list(self, dir_name, whitelist):
    outputList = []
for root, dirs, files in os.walk(dir_name):
    for f in files:
        if os.path.splitext(f)[1] in whitelist:
            outputList.append(os.path.join(root, f))
else:
    self._email_to_('ignore')
break
return outputList
os.walk without digging into directories below