Django group by hour | 易学教程

问题

I have the following model in Django.

class StoreVideoEventSummary(models.Model):
    Customer = models.ForeignKey(GlobalCustomerDirectory, null=True, db_column='CustomerID', blank=True, db_index=True)
    Store = models.ForeignKey(Store, null=True, db_column='StoreID', blank=True, related_name="VideoEventSummary")
    Timestamp = models.DateTimeField(null=True, blank=True, db_index=True)
    PeopleCount = models.IntegerField(null=True, blank=True)

I would like to find out the number of people entering the store each hour.

To achieve this, I'm trying to group the rows by the hour on Timestamp and sum the PeopleCount column.

store_count_events = StoreVideoEventSummary.objects.filter(Timestamp__range=(start_time, end_time),
                                                       Customer__id=customer_id,
                                                       Store__StoreName=store)\
        .order_by("Timestamp")\
        .extra({
            "hour": "date_part(\'hour\', \"Timestamp\")"
        }).annotate(TotalPeople=Sum("PeopleCount"))

This doesn't seem to group the results by the hour, it merely adds a new column TotalPeople which has the same value as PeopleCount to each row in the query set.

回答1:

just break it into two steps

objs = StoreVideoEventSummary.objects.filter(Timestamp__range=(start_time, end_time),
                                                   Customer__id=customer_id,
                                                   Store__StoreName=store)\
    .order_by("Timestamp")

def date_hour(timestamp):
   return datetime.datetime.fromtimestamp(timestamp).strftime("%x %H")

groups = itertools.groupby(objs, lambda x:date_hour(x.Timestamp))
#since groups is an iterator and not a list you have not yet traversed the list
for group,matches in groups: #now you are traversing the list ...
    print group,"TTL:",sum(1 for _ in matches)

this allows you to group by several distinct criteria

if you just want the hour regardless of date just change date_hour

def date_hour(timestamp):
   return datetime.datetime.fromtimestamp(timestamp).strftime("%H")

if you wanted to group by day of the week you just use

def date_hour(timestamp):
   return datetime.datetime.fromtimestamp(timestamp).strftime("%w %H")

回答2:

Building off your original code, could you try:

store_count_events = StoreVideoEventSummary.objects.filter(Timestamp__range=(start_time, end_time), Customer__id=customer_id, Store__StoreName=store)\
    .extra({
        "hour": "date_part(\'hour\', \"Timestamp\")"
    })\
    .values("hour")\
    .group_by("hour")\
    .annotate(TotalPeople=Sum("PeopleCount"))

回答3:

I know I'm late here, but taking cues from the doc, https://docs.djangoproject.com/en/1.11/ref/models/querysets/#django.db.models.query.QuerySet.extra

the below filter should work for you.

store_count_events = StoreVideoEventSummary.objects.filter(
    Timestamp__range=(start_time, end_time),
    Customer__id=customer_id,
    Store__StoreName=store
).order_by(
    'Timestamp'
).extra(
    select={
        'hour': 'hour(Timestamp)'
    }
).values(
    'hour'
).annotate(
    TotalPeople=Sum('PeopleCount')
)

来源：https://stackoverflow.com/questions/30465013/django-group-by-hour

标签

python

django

orm

group-by