sqlAlchemy 按DateTime字段的年或月进行group_by查询

　　month_field=extract('month',User.create_date)==month
　　year_field=extract('year',User.create_date)==year

　　between=User.create_date.between("2016-6-500:00:00","2016-6-1500:00:00")
　　counts=session.query(day,func.count('*')).filter(month_field,year_field,between).group_by('day').all()
　　end=datetime.now()
　　start=datetime.now()+timedelta(days=-int(time_section))
　　between=User.create_date.between(start,end).注意start和end