datetime的小坑

在做悦运动这个项目时，在创建约运动关系表时，运动开始时间，注意（导入datetime包时，我导入的是class datetime(__datetime.date)这个类，可以调用这个类中的方法，调用当前时间直接可以调用datetime.now()

 from datetime import datetime
 ......
 class Schedule(models.Model):
     '''
     发起约运动
     '''
     Status = ((1, '已完成'), (2, '待人加入'), (3, '已取消'))
     user = models.ForeignKey(UserProfile, on_delete=models.CASCADE, verbose_name='发起人')
     join_type = models.BooleanField(verbose_name='是否发起人')
     now_people = models.IntegerField(verbose_name='已有人数', null=True, blank=True)
     school = models.ForeignKey(Schools, on_delete=models.CASCADE, verbose_name='学校', default='')
     sport = models.ForeignKey(Sports, on_delete=models.CASCADE, verbose_name='运动项目')
     address = models.CharField(verbose_name='约定地点', max_length=100)
     sport_time = models.DateTimeField(verbose_name='约定运动开始时间')
     sport_end_time = models.DateTimeField(verbose_name='约定运动结束时间', default='')
     people_nums = models.IntegerField(verbose_name='人数')
     add_time = models.DateTimeField(default=datetime.now, verbose_name='添加时间')
     status = models.IntegerField(choices=Status, verbose_name='状态')

     class Meta:
         verbose_name = '发起约运动'
         verbose_name_plural = verbose_name

     def __str__(self):
         return self.sport.sport_name + '-' + str(self.sport_time)

 class JoinSchedule(models.Model):
     '''
     加入的运动
     '''
     schedule = models.ForeignKey(Schedule, on_delete=models.CASCADE, verbose_name='加入的运动')
     user = models.ForeignKey(UserProfile, on_delete=models.CASCADE, verbose_name='用户')
     add_time = models.DateTimeField(default=datetime.now, verbose_name='添加时间')

     class Meta:
         verbose_name = '加入运动'
         verbose_name_plural = verbose_name

     def __str__(self):
         return str(self.schedule_id) + '--' + str(self.user_id)

而在序列化该表时，导入的是datetime:class datetime,包含了datetime这个模块所有方法，获得当前时间可以datetime.datetime.now(),如第十五行

 import datetime
 class MyJoinScheduleSerializer(serializers.ModelSerializer):
     '''
     加入约运动序列化
     '''
     user = serializers.HiddenField(default=serializers.CurrentUserDefault())
     add_time = serializers.DateTimeField(read_only=True, format='%Y-%m-%d %H:%M:%S')

     def create(self, validated_data):
         user = self.context['request'].user
         schedule = validated_data['schedule']
         if Schedule.objects.filter(user=schedule.user, id=schedule.id).first().user == user:
             raise serializers.ValidationError('您是该运动的发起人，已默认加入')
         double_status = False
         schedules = JoinSchedule.objects.filter(user=user,schedule__sport_time__gt=datetime.datetime.now())
         if schedules:
             for s in schedules:
                 if s.schedule.sport_time > schedule.sport_end_time or schedule.sport_time >= s.schedule.sport_end_time:
                     pass
                 else:
                     double_status = True
                     break
         if double_status:
             raise serializers.ValidationError({"time_error":"与你已有的预约运动时间冲突"})
         else:
             existed = JoinSchedule.objects.create(**validated_data)
         return existed

     class Meta:
         model = JoinSchedule
         fields = '__all__'
         validators = [
             UniqueTogetherValidator(
                 queryset=JoinSchedule.objects.all(),
                 fields=('user', 'schedule'),
                 message='已经加入'
             )
         ]

运行测试时会报错;type object 'datetime.datetime' has no attribute 'datetime'（对象'datetime.datetime'类型没有属性'datetime'）,原因：

from datetime import datetime 已经相当于把命名空间引入到datetime.datetime一层，而在序列化时，又是import datetime,调用datetime.datetime.noe()会让编译器在datetime.datetime空间下去找datetime类。

但是datetime类是应该在datetime空间下的,所以会报错，主要是由于两个datetime不是一个等级的。