Question

我有这个

b_articles = tc.tc_buch_articles.all()
j_articles = tc.tc_journal_articles.all()                
joined = itertools.chain(b_articles, j_articles)
sorter = lambda x: x.article_in_collection__year if hasattr(x, 'article_in_collection__year') else x.article_in_journal__year
articles = sorted(joined, key = sorter, reverse=True)

以下是我的模特

我收到错误：

'EntryArticleInCollection' object has no attribute 'article_in_journal__year'

我想达到这样的结果：

a = 1, 3, 8, 10
b = 2, 3, 5, 12
res = 1, 2, 3, 3, 5, 8, 10, 12

模特：

class TopicCenter(models.Model):
  user = models.ForeignKey(Person,related_name="user_tcs")      
  title = models.TextField()
  subtitle = models.TextField()

class ArticleInCollection(models.Model):
  user = models.ForeignKey(Person,related_name="user_buchaufsatz")
  title = models.TextField()
  book = models.ForeignKey(Book,related_name="book_aufsatze")    
  added = models.DateTimeField(auto_now_add=True, blank=True)
  year = models.IntegerField(default=0000)

class ArticleInJournal(models.Model):
  user = models.ForeignKey(Person,related_name="user_journalaufsatz")
  title = models.TextField()
  journal = models.ForeignKey(Journal,related_name="journal_aufsatze")
  added = models.DateTimeField(auto_now_add=True, blank=True)
  year = models.IntegerField(default=0000)

class EntryArticleInCollection(models.Model):
  added = models.DateTimeField(auto_now_add=True, blank=True)
  lastmodified = models.DateTimeField(auto_now=True, blank=True)
  topiccenter = models.ForeignKey(TopicCenter,related_name="tc_buch_articles")
  article_in_collection = models.ForeignKey(ArticleInCollection,related_name="bucharticle_entries")

class EntryArticleInJournal(models.Model):
  added = models.DateTimeField(auto_now_add=True, blank=True)
  lastmodified = models.DateTimeField(auto_now=True, blank=True)
  topiccenter = models.ForeignKey(TopicCenter,related_name="tc_journal_articles")
  article_in_journal = models.ForeignKey(ArticleInJournal,related_name="journal_article_entries")

Answer 1

这种getattr()方法怎么样：

sorter = lambda x: getattr(x, 'article_in_collection', x.article_in_journal).year

或：

def sorter(x): 
    try: 
        return x.article_in_collection.year 
    except AttributeError: 
        return x.article_in_journal.year

您的解决方案的问题在于您首先需要获取ForeignKey字段，然后通过dot notation获取相关模型上的字段。在这种情况下，双下划线方法不起作用。

python排序和链 - Django查询集

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