python - 多个 For 循环 Django

Question

我有以下两个模型 ASPBoookings 和 Athlete。 Athlete 模型通过名为 athlete 的外键链接到 ASPBookings 模型。
我正在尝试创建一个循环，循环遍历 ASPBooking 表中的所有预订，并找出每个运动员最近的预订。 (该表可以包含针对相同或不同运动员 (athlete_id) 的多个预订 一旦我获得此信息 (booking_date 和 athlete_id) 然后我希望能够自动更新 ”运动员模型中的最新 ASP session 字段”。
这是我到目前为止所尝试的。我可以循环浏览 ASPBookings 表中的预订，并使用 booking_date 和 athlete_id 检索和更新“最新 ASP session 字段”，但我不能对表中的多个不同运动员执行此操作。目前，该 View 仅识别最新预订和分配的 athlete_id，然后更新该字段。
在此先感谢您的帮助。
下面是代码:
ASPBookings 模型

class ASPBookings(models.Model):
    asp_booking_ref = models.CharField(max_length=10, default=1)
    program_type = models.CharField(max_length=120, default='asp')
    booking_date = models.DateField()
    booking_time = models.CharField(max_length=10, choices=booking_times)
    duration = models.CharField(max_length=10, choices=durations, default='0.5')
    street = models.CharField(max_length=120)
    suburb = models.CharField(max_length=120)
    region = models.CharField(max_length=120, choices=regions, default='Metro')
    post_code = models.CharField(max_length=40)
    organisation_type = models.CharField(max_length=120,choices=organisation_types, default='Government School')
    audience_number = models.CharField(max_length=10)
    presentation_form = models.CharField(max_length=120, choices=presentation_form_options, default='Face to Face')
    contact_name = models.CharField(max_length=80)
    email = models.EmailField()
    phone_number = models.CharField(max_length=120)
    comments = models.TextField()
    status = models.CharField(max_length=80, choices=statuses, default='TBC')
    email_sent = models.BooleanField(default=False)
    athlete = models.ForeignKey(Athlete, default= '1', on_delete=models.CASCADE)

    def __str__(self):
        return self.contact_name
        
    # return URL after the POST has been submitted.
    def get_absolute_url(self):
        return reverse('vistours:success')

运动员模型

class Athlete(models.Model):
    athlete_ref = models.CharField(max_length=10, default=1)
    athlete_name = models.CharField(max_length=80)
    email = models.EmailField()
    phone_number = models.CharField(max_length=120)
    home = models.CharField(max_length=120)
    education = models.CharField(max_length=120)
    sport = models.CharField(max_length=120, choices=sports, default='1500m Runner')
    notes = models.TextField(default='None')
    gender = models.CharField(max_length=120, choices=genders, default='Not Specified')
    para_athlete = models.BooleanField(blank=True)
    working_with_children = models.BooleanField(blank=True)
    expiry_date = models.DateField(blank=True, null=True)
    available = models.BooleanField(blank=True)
    available_from = models.DateField(blank=True, null=True)
    bfbw = models.BooleanField(blank=True)
    latest_bfbw_session = models.DateField(blank=True, null=True)
    number_bfbw_sessions = models.CharField(blank=True, null=True, max_length=10)
    asp = models.BooleanField(blank=True)
    latest_asp_session = models.DateField(blank=True, null=True)
    number_asp_sessions = models.CharField(blank=True, null=True, max_length=10)
    tours = models.BooleanField(blank=True)
    latest_tours_session = models.DateField(blank=True, null=True)
    number_tours_sessions = models.CharField(blank=True, null=True, max_length=10)

    def __str__(self):
        return self.athlete_name

    # return URL after the POST has been submitted.
    def get_absolute_url(self):
        return reverse('home')

查看

# Complete first loop for inital values.
    for date in asp_data:
        if date.booking_date != None:
            first_loop = date.booking_date
            athl_id = date.athlete_id
            break
    # If next value is greater than inital value, replace current values.      
    for date in asp_data:
        if date.booking_date != None:
            if date.booking_date > first_loop:
                first_loop = date.booking_date
                athl_id = date.athlete_id
    

    print(first_loop)
    print(athl_id)

    update_date = Athlete.objects.get(id=athl_id)
    update_date.latest_asp_session = first_loop
    update_date.save()

Answer 1

不需要循环。您可以使用子查询一次性为所有运动员执行此操作，将所有繁重的工作都留给您的数据库:

from django.db.models import F, OuterRef, Subquery

bookings = ASPBookings.objects.filter(
    athlete=OuterRef('pk')
).order_by('-booking_date')

Athlete.objects.annotate(
    latest_asp_booking_date=Subquery(
        bookings.values('booking_date')[:1]
    )
).update(
    latest_asp_session=F('latest_asp_booking_date')
)