根据日期和时间创建对象

Question

我有一个 Event 模型，每个事件会有不同的节目。

class Event(models.Model):
    title = models.CharField(max_length=200)

class Show(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    date_time = models.DateTimeField(unique=True)

我有另一个 Ticket 模型。每张票都应该是独一无二的。这意味着每张门票都是独一无二的，并且与表演和座位相关。

class Ticket(models.Model):
    show = models.ForeignKey(Show)
    seat = models.ForeignKey(Seat)

    class Meta:
        unique_together = ('show', 'seat')

我需要根据用户提供的开始日期和结束日期创建节目。假设这是一个 JSON 帖子：

{
    "event_id": 1,
    "start_date": "2018-02-16",
    "end_date": "2018-02-20",
    "time_list": ["11:00 AM", "8:00 PM"]
}

从上面的 JSON 示例中，我需要像这样开始创建 Show：

# Start with the start_date as the date, and for each time from the time_list
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-16 11:00 AM', "%Y-%m-%d %I:%M %p")
)
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-16 8:00 PM', "%Y-%m-%d %I:%M %p")
)
# Next date after the start_date, i.e., 16+1 = 17
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-17 8:00 PM', "%Y-%m-%d %I:%M %p")
)
.
.
.
# Create Show objects till the end_date and for each time from the time_list
Show.objects.create(
    event = 1,
    date_time = datetime.strptime('2018-02-20 8:00 PM', "%Y-%m-%d %I:%M %p")
)

现在这就是我创建 Show 对象的方式：

def create_show_by_datetime(self, request):
    event_id = request.data['event_id']
    try:
        event = Event.objects.get(id=event_id)
    except Event.DoesNotExist:
        return Response(
            {'error': 'event with id: %s does not exist.' % event_id},
            status=status.HTTP_400_BAD_REQUEST
        )

    start_date = request.data['start_date']
    end_date = request.data['end_date']
    time_list = request.data['time_list']
    date_format = '%Y-%m-%d'
    time_format = "%I:%M %p"
    try:
        datetime.strptime(start_date, date_format)
        datetime.strptime(end_date, date_format)
        for i in range(len(time_list)):
            time = datetime.strptime(time_list[i], time_format)
    except ValueError as e:
        return Response(
            {'error': 'Time was not in a supported format. %s' % e},
            status=status.HTTP_400_BAD_REQUEST
        )

    delta_days = datetime.strptime(end_date, date_format).date() - datetime.strptime(start_date, date_format).date()
    delta_days = delta_days.days + 1
    dt = None
    try:
        with transaction.atomic():
            for i in range(delta_days):
                day = datetime.strptime(start_date, date_format) + timedelta(days=i)
                for i in range(len(time_list)):
                    hrs = datetime.strptime(time_list[i], time_format).hour
                    mins = datetime.strptime(time_list[i], time_format).minute
                    dt = day + timedelta(hours=hrs, minutes=mins)
                    show = Show.objects.create(
                        event=event,
                        date_time=dt
                    )
            return Response({"data": 'Post succesfull'}, status=status.HTTP_201_CREATED)
    except IntegrityError as e:
        return Response(
            {
                'error': "event with date and time already exsits. %s-%s-%s at %s:%s" % (
                    dt.day, dt.month, dt.year, dt.hour, dt.minute),
                'detail': str(e)
            }, status=status.HTTP_400_BAD_REQUEST

但我希望有比我现在做的更优雅的方式。我正在使用 python 3、django 2 和 django rest 框架。如何根据event_id、start_date、end_date 和time_list 创建带有事件的Show和日期时间？

Answer 1

我的方法有点不同。您在问题标签中说您正在使用django-rest-framework.. 那么序列化程序在哪里？ :)

让我们创建两个序列化器，一个用于用户数据验证（因为我们不信任 USER！），另一个用于多数据插入。

我还没有检查代码！但是你可以用它作为一个例子......

class ShowEventSerializer(serializers.Serializer):
    event_id = serializers.IntegerField()
    start_date = serializers.DateField(required=True)
    end_date = serializers.DateField(required=True)
    time_list = serializers.ListField(
        child=serializers.TimeField()
    )

    class Meta:
        fields = ('event_id', 'start_date', 'end_date', 'time_list')

class ShowSerializer(serializers.Serializer):
    date_time = serializers.DateTimeField()

    class Meta:
        model = Show
        fields = ('event', 'date_time')

现在，使用序列化器，我们将验证用户数据，然后创建一个 json 数据对象：

def create_show_by_datetime(self, request):

    show_event_serializer = ShowEventSerializer(data=request.data)
    if not show_event_serializer.is_valid():
        return Response({'error': show_event_serializer.errors},status=status.HTTP_400_BAD_REQUEST)

    event_id = show_event_serializer.data['event_id']
    try:
        event = Event.objects.get(id=event_id)
    except Event.DoesNotExist:
        return Response({'error': 'event with id: %s does not exist.' % event_id},status=status.HTTP_400_BAD_REQUEST)

    start_date = show_event_serializer.data['start_date']
    end_date = show_event_serializer.data['end_date']
    time_list = show_event_serializer.data['time_list']
    date_format = '%Y-%m-%d'
    time_format = "%I:%M %p"

    try:
        datetime.strptime(start_date, date_format)
        datetime.strptime(end_date, date_format)
        for i in range(len(time_list)):
            time = datetime.strptime(time_list[i], time_format)
    except ValueError as e:
        return Response(
            {'error': 'Time was not in a supported format. %s' % e},
            status=status.HTTP_400_BAD_REQUEST
        )

    delta_days = datetime.strptime(end_date, date_format).date() - datetime.strptime(start_date, date_format).date()
    delta_days = delta_days.days + 1
    dt = None
    show_data = []
    for i in range(delta_days):
        day = datetime.strptime(start_date, date_format) + timedelta(days=i)
        for i in range(len(time_list)):
            hrs = datetime.strptime(time_list[i], time_format).hour
            mins = datetime.strptime(time_list[i], time_format).minute
            dt = day + timedelta(hours=hrs, minutes=mins)
            show_data.append({
                "event": event,
                "date_time": dt
            })

    try:
        with transaction.atomic():
            show_serializer = ShowSerializer(data=show_data, many=True)
            if show_serializer.is_valid():
                show_serializer.save()

            return Response({"data": 'Post succesfull'}, status=status.HTTP_201_CREATED)
    except IntegrityError as e:
        return Response(
            {
                'error': "event with date and time already exsits. %s-%s-%s at %s:%s" % (
                    dt.day, dt.month, dt.year, dt.hour, dt.minute),
                'detail': str(e)
            }, status=status.HTTP_400_BAD_REQUEST

所以这段代码和你的基本相同，只是使用 DRF 保存对象的方式不同。查看show_data 变量。

这个解决方案只是看待问题的另一种方式。

祝你好运！

http://www.django-rest-framework.org/api-guide/serializers/

http://www.django-rest-framework.org/api-guide/fields/

Answer 2

那么你的Show 模型应该是这样的

from django.contrib.postgres.fields import ArrayField

class Show(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    start_date = models.DateField(blank=True, null=True)
    end_date = models.DateField(blank=True, null=True)
    board = ArrayField(
        models.TimeField(blank=True, null=True),
        size=10, # specify max array size
    )

因此您将拥有具有指定 DateFields 和 TimeFields 数组的模型 Show。

django 文档：Array Field、Time Field、Date Field

Answer 3

日期时间库中有一些工具可以为您提供更简化的方法来生成时间。您可以使用toordinal 将日期转换为整数，使用fromordinal 将整数转换回日期；这是创建一系列日期的好方法。您可以使用combine 将date 对象和time 对象合并为datetime。我会创建以下函数：

from datetime import datetime, date

def get_showtimes(post):
    start = datetime.strptime(post['start_date'], '%Y-%m-%d')
    end = datetime.strptime(post['end_date'], '%Y-%m-%d')
    times = [datetime.strptime(t, '%I:%M %p').time() for t in post['time_list']]
    for ordinal in range(start.toordinal(), end.toordinal() + 1):
        date = date.fromordinal(date)
        for time in times:
            yield datetime.combine(date, time)

然后，在您的代码中，替换第二个 try: except: 块及其后面的内容：

try:
    showtimes = list(get_showtimes(post))
except ValueError as e:
    return Response(
        {'error': 'Time was not in a supported format. %s' % e},
        status=status.HTTP_400_BAD_REQUEST
    )

try:
    with transaction.atomic():
        for showtime in showtimes:
            show = Show.objects.create(event=event, date_time=showtime)
except IntegrityError as e:
    # etc.

Answer 4

我将离开验证部分，只专注于从给定数据生成 Show 对象：

data = request.data

date_format = '%Y-%m-%d'
time_format = "%I:%M %p"
show_time_format = f"{date_format} {time_format}"

# get the total number of days by parsing start and end dates
start_date = datetime.strptime(data['start_date'], date_format)
end_date = datetime.strptime(data['end_date'], date_format)
total_days = (end_date - start_date).days + 1

# Get the timings for the first day.
# We will use this to generate the timings for the rest of the days.
first_day_timings = [
    datetime.strptime(f"{data['start_date']} {show_time}", show_time_format)
    for show_time in data['time_list']
]

# generate all show objects using list comprehension and bulk create later
show_objects = [
    Show(event=event, date_time=first_day_timing + timedelta(days=day_cnt))
    for day_cnt in range(total_days)
    for first_day_timing in first_day_timings
]

Show.objects.bulk_create(show_objects)

对现有代码的改进：

1. 减少了解析日期/时间和计算小时/分钟的实例数。
2. 使用列表推导生成显示对象和批量创建，而不是在事务中一次创建一个对象。