(RESOLVED) How to get only the last month's records present in the database, using queryset dja-CodePudding

I need to get only the objects of the last month present in the DB. I don't mean the last 30 days or the last calendar month, but the most recent month recorded in the database... I've seen that django has the latest() function that returns the most recent object in the table based on in the given field(s), however I want it to return multiple objects based on the given month.

revisoes = Revisao.objects.filter(apicultor__in=apicultores).order_by('-data_registro')

This is the queryset I'm using, only it returns all revisions for a given beekeeper. I need it to return only revisions based on the last month of the "data_registro" field

CodePudding user response：

You can determine the previous month with a relativedelta object [readthedocs.io] of the dateutil package [readthedocs.io] and use this to retrieve items from the last month:

from dateutil.relativedelta import relativedelta
from django.utils.timezone import now

revisoes = Revisao.objects.filter(
    apicultor__in=apicultores, data_registro__gte=now()-relativedelta(months=1)
).order_by('-data_registro')

or if you want to retrieve items since the beginning of the month, you use:

from calendar import monthrange
from datetime import datetime

some_datetime = datetime(2022, 1, 28, 15, 15)
start = some_datetime.date().replace(day=1)
end = some_datetime.date().replace(day=monthrange(some_datetime.year, some_datetime.month)[1])

revisoes = Revisao.objects.filter(
    apicultor__in=apicultores, data_registro__range=[start, end]
).order_by('-data_registro')

or if data_registro is a DateTimeField:

from calendar import monthrange
from datetime import datetime

some_datetime = datetime(2022, 1, 28, 15, 15)
start = some_datetime.date().replace(day=1)
end = some_datetime.date().replace(day=monthrange(some_datetime.year, some_datetime.month)[1])

revisoes = Revisao.objects.filter(
    apicultor__in=apicultores, data_registro__date__range=[start, end]
).order_by('-data_registro')

CodePudding user response：

SOLUTION: I solved my problem as follows:

meses = [obj.data_registro for obj in revisoes]
ultimo_mes = max(meses)
ultimo_mes = ultimo_mes.strftime("%Y-%m")
revisoes_recentes = Revisao.objects.filter(apicultor__in=apicultores, data_registro__contains=ultimo_mes)