基于日期w / Django ORM查询值 [英] query for values based on date w/ Django ORM

问题描述

我有一堆具有值和日期字段的对象：

  obj1 = Obj（date ='2009 -8-20'，value = 10）
 obj2 = Obj（date ='2009-8-21'，value = 15）
 obj3 = Obj（date ='2009-8-23'值= 8）
  

我想要返回：

  [10，15，0，8] 
  

或更好，总共到达这一点：

  [10，25，25，33] 
  

我最好直接从数据库获取此数据，但否则我可以很容易地使用for / p>

我正在使用Django的ORM和Postgres

编辑：

只是要注意，我的例子只涵盖了几天，但在实践中，我有几百个对象覆盖了几十年...我正在做的是创建一个线图，显示所有对象的总和随着时间的推移而增长（很长一段时间）

解决方案

这个没有测试，因为设置一个Django表来测试是有点太痛苦：

  from datetime import date，timedelta 
＃http://www.ianlewis.org/en/python-date-range-iterator 
 def datetimeRange（from_date，to_date = None）：
而to_date是None或from_date< = to_date：
 yield from_date 
 from_date = from_date + timedelta（days = 1）
 
 start = date（2009，8，20）
 end = date（2009，8，23）
 objects = Obj.objects.filter（date__gte = start）
 objects = objects。过滤器（date__lte = end）
 
结果= {} 
对象中的o：
结果[o.date] = o.value 
 
返回[date.get（day，0）for day in datetimeRange（start，end）] 
  

每天运行一个单独的查询。

I have a bunch of objects that have a value and a date field:

obj1 = Obj(date='2009-8-20', value=10)
obj2 = Obj(date='2009-8-21', value=15)
obj3 = Obj(date='2009-8-23', value=8)

I want this returned:

[10, 15, 0, 8]

or better yet, an aggregate of the total up to that point:

[10, 25, 25, 33]

I would be best to get this data directly from the database, but otherwise I can do the totaling pretty easily with a forloop.

I'm using Django's ORM and also Postgres

edit:

Just to note, that my example only covers a few days, but in practice, I have hundreds of objects covering a couple decades... What I'm trying to do is create a line graph showing how the sum of all my objects has grown over time (a very long time)

解决方案

This one isn't tested, since it's a bit too much of a pain to set up a Django table to test with:

from datetime import date, timedelta
# http://www.ianlewis.org/en/python-date-range-iterator
def datetimeRange(from_date, to_date=None):
    while to_date is None or from_date <= to_date:
        yield from_date
        from_date = from_date + timedelta(days = 1)

start = date(2009, 8, 20)
end = date(2009, 8, 23)
objects = Obj.objects.filter(date__gte=start)
objects = objects.filter(date__lte=end)

results = {}
for o in objects:
    results[o.date] = o.value

return [results.get(day, 0) for day in datetimeRange(start, end)]

This avoids running a separate query for every day.

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