如何使用列表理解根据字长筛选字符串列表？

Question

我正在尝试筛选字符串列表中等于1个字符或2个字符的单词。这是我的样本数据-

l = ['new vaccine tech long term testing',
    'concerned past negative effects vaccines flu shot b',
    'standard initial screening tb never tb chest x ray']

我试着写这个逻辑，但不知怎么的，输出结果是一个单词列表，而不是句子列表

cleaner = [ ''.join(word) for each in l for word in each.split() if len(word) > 2 ]


cleaner
['new',
 'vaccine',
 'tech',
 'long',
 'term',
 'testing',
 'concerned',
 'past',
 'negative',
 'effects',
 'vaccines',
 'flu',
 'shot',
 'standard',
 'initial',
 'screening',
 'never',
 'chest',
 'ray']

如何使其输出如下

output = ['new vaccine tech long term testing',
    'concerned past negative effects vaccines flu shot',
    'standard initial screening never chest ray']

Answer 1

您需要使用嵌套列表理解，而不是单个列表理解。外层是句子，内层是单词

你需要用空格连接，而不是空字符串，在单词之间加空格

output = [' '.join([word for word in sentence.split() if len(word) > 2]) for sentence in l]

Answer 2

您可以进行筛选以获得字符串的特定大小的单词，然后将其加入到列表中

l = ['new vaccine tech long term testing',
     'concerned past negative effects vaccines flu shot b',
     'standard initial screening tb never tb chest x ray']
res = [" ".join(filter(lambda x: len(x) > 2, eaach.split(' '))) for eaach in l]
print(res)