以下行产生现有数据点的列表:
datapoint_list = organisation.datapoint_set.filter(timestamp__gte=startDate, timestamp__lte=endDate)
我想以JSON格式
return
的日期从startDate
到lastDate
,对于这些日期没有现有的数据点。如何才能做到这一点?
我最好的主意是:
class Missing(generics.ListAPIView)
...
queryset = organisation.datapoint_set.filter(timestamp__gte=startDate, timestamp__lte=endDate)
Loop over the datesdelta
Loop over the datapoints
If datapoint.timestamp == datedelta.timestamp then
Push timestamp to object
Continue
End if
End loop
End loop
Return object
但是我还没有成功实现日期循环。也许还有更简单的方法可以做到这一点?
编辑:
datedelta是根据查询参数确定的,默认情况下应在上周寻找缺失的数据点:
days = int(self.request.query_params.get('days', 7))
startDate = datetime.today() - timedelta(days)
endDate = datetime.today()
查询集包含:
<DataPoint: Value: 123, Timestamp: 2015-12-15>
<DataPoint: Value: 123, Timestamp: 2015-12-11>
<DataPoint: Value: 123, Timestamp: 2015-12-10>
<DataPoint: Value: 123, Timestamp: 2015-12-09>
<DataPoint: Value: 123, Timestamp: 2015-12-08>
JSON输出应类似于
[
'date': '2015-12-16',
'date': '2015-12-14',
'date': '2015-12-13',
'date': '2015-12-12',
'date': '2015-11-07'
}
我的问题是如何从该查询集获得该输出。
最佳答案
set()
学习使用它,您将统治世界!首先,根据您向您展示的示例,您仅对日期稍作修改即可查询日期,因此可以提高查询效率:
queryset = organisation.datapoint_set.filter(timestamp__gte=startDate, timestamp__lte=endDate).values_list('timestamp', flat=True)
完成后,将如下所示:
queryset = [datetime(2015,12,15), datetime(2015,12,11), datetime(2015,12,10), datetime(2015,12,9), datetime(2015,12,8)]
现在,我们生成所需的值:
>>> set([endDate - timedelta(x) for x in xrange(days)])
set([datetime.date(2015, 12, 14), datetime.date(2015, 12, 16), datetime.date(2015, 12, 15), datetime.date(2015, 12, 12), datetime.date(2015, 12, 13), datetime.date(2015, 12, 10), datetime.date(2015, 12, 11)])
完美,我们(减去它们)
-
:>>> set([endDate - timedelta(x) for x in xrange(days)]) - set(queryset)
set([datetime.date(2015, 12, 14), datetime.date(2015, 12, 16), datetime.date(2015, 12, 15), datetime.date(2015, 12, 12), datetime.date(2015, 12, 13), datetime.date(2015, 12, 10), datetime.date(2015, 12, 11)])
让一切变得漂亮:
import datetime
days = 10
# a bit of a hack to get the current date without any time stuff.
endDate = datetime.datetime.combine(datetime.date.today(), datetime.datetime.min.time())
queryset = [datetime.datetime(2015,12,15), datetime.datetime(2015,12,11), datetime.datetime(2015,12,10), datetime.datetime(2015,12,9), datetime.datetime(2015,12,8)]
date_ranges = set([endDate - datetime.timedelta(x) for x in xrange(days)])
output = sorted(list(date_ranges - set(queryset)))
print([x.strftime('%Y-%m-%d') for x in output])
输出为:
['2015-12-07', '2015-12-12', '2015-12-13', '2015-12-14', '2015-12-16']
如果您将时间戳记作为
date
对象使用,则更加简单:import datetime
days = 10
endDate = datetime.date.today()
queryset = [datetime.date(2015,12,15), datetime.date(2015,12,11), datetime.date(2015,12,10), datetime.date(2015,12,9), datetime.date(2015,12,8)]
date_ranges = set([endDate - datetime.timedelta(x) for x in xrange(days)])
output = sorted(list(date_ranges - set(queryset)))
print([x.strftime('%Y-%m-%d') for x in output])