优雅的方式来过滤无或不过滤

Question

以下SQLAlchemy代码可以正常工作，但看起来不是pythonic：

if has_died: # has_died: True or False
  query = query.filter(User.died_at != None)
else:
  query = query.filter(User.died_at == None)

添加过滤器的更优雅方式是什么？

Answer 1

嗯，你可以这样做：

query = query.filter((User.died_at != None) if has_died else (User.died_at == None))

但它有点难以阅读。我想你是怎么做的。

Answer 2

您可以将其重写为一行ternary operator

query = query.filter((User.died_at != None) if has_died else (User.died_at == None))

Answer 3

怎么样：

query = query.filter(bool(User.died_at) == has_died)

它返回：

• False如果User.died_at为None且has_died为True
• True如果User.died_at为None且has_died为False
• True如果User.died_at不是None且has_died是True
• False如果User.died_at不是None且has_died是False

这是预期的行为......

但话又说回来，不确定它比你的代码更容易理解！