在Django中使用mongoengine。 无法将文档实例保存到数据库中

Question

I am trying to create new Document and save it to the database. The database in Mongo was created automatically, but no entries are saved. What I am trying to do in my code is the following:

lesson = Lesson()
lesson.group = Group(group_name='KP-32')
lesson.teacher = Teacher(teacher_name='Vasia')
lesson.room = Room(room_number=32, building_number=323)
lesson.subject = Subject(subject_code=03321, subject_name='Math', hours=33)
lesson.save()
ls = []
for lesson in Lesson.objects:
    ls.append(lesson)

But as soon as I try to display ls, I receive in my view (displaying ls) only: id subject teacher group room (names of references???) and nothing is stored into the db. Hope to hear some solution for my problem and thanks in advance.

Settings

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.dummy',
    }
}
mongoengine.connect('jack', host='127.0.0.1', port=27017)

AUTHENTICATION_BACKENDS = (
    'mongoengine.django.auth.MongoEngineBackend',
)
SESSION_ENGINE = 'mongoengine.django.sessions'

Models

from mongoengine import *

    class Room(EmbeddedDocument):
        room_number = IntField(default=0)
        building_number = IntField(default=0)
        capacity = IntField(default=0, required=False)

        def __unicode__(self):
            return smart_unicode("Room #%d" % self.room_number)


    class Teacher(EmbeddedDocument):
        teacher_name = StringField(max_length=60)
        phone = StringField(max_length=15, required=False)
        email = StringField(required=False)

        def __unicode__(self):
            return smart_unicode(self.teacher_name)


    class Subject(EmbeddedDocument):
        subject_code = IntField()
        subject_name = StringField(max_length=60)
        hours = IntField(required=False)

        def __unicode__(self):
            return smart_unicode(self.subject_name)


    class Group(EmbeddedDocument):
        group_name = StringField(max_length=20)
        specialization = StringField(max_length=60, required=False)
        student_count = IntField(required=False)

        def __unicode__(self):
            return smart_unicode(self.group_name)


    class Lesson(Document):
        subject = EmbeddedDocumentField(Subject)
        teacher = EmbeddedDocumentField(Teacher)
        group = EmbeddedDocumentField(Group)
        room = EmbeddedDocumentField(Room)
        attendance = IntField()

        def __unicode__(self):
            return smart_unicode("Lesson #%d" % self.id)

Answer 1

Database is created when this line is executed

mongoengine.connect('jack', host='127.0.0.1', port=27017)

Also it is working for me.

Can you just print the output of this for me:

ls[0].__dict__