Question

python 中 return list 得到none

class alexicon(object):

def __init__(self):
self.items = []

def scan(self, words):
self.word = words.split()
# direction
self.direction_word = [i for i in self.word if i in self.directions]
self.direction_list = []
for x in self.direction_word:
self.direction_list.append(('direction', '%s' %(x)) )
if self.direction_list != []:
self.items.extend(self.direction_list)
else:
pass

return self.items

为什么执行这个类后得到的都是None。
如果我直接print alexicon.items里是有元素的。

Answer 1

self.directions没赋过值。