詳解python中mongoengine庫用法

目錄

• 一、MongoDB得安裝與連接
• 二、MongoEngine模型介紹
• 2.1、ODM模型介紹
• 2.2、常見數據類型
•  2.3、數據類型通用參數
• 2.4、類屬性meta常見配置項
• 2.5、文檔得嵌套模型
•  三、添加數據
• 3.1、方式一
• 3.2、方式二：使用create()方法
• 四、查詢數據
• 4.1、單個文檔查詢
• 4.2、條件查詢
• 4.3、聚合統計
•  4.4、排序
•  4.5、分頁處理
•  五、修改和刪除數據
• 5.1、修改數據
• 5.2、刪除數據

一、MongoDB得安裝與連接

安裝：pip install mongoengine

連接mongodb數據庫

from pymongo import MongoClientcli = MongoClient('192.168.124.104', 27017)mongodb = cli['test']print(mongodb)

from mongoengine import connect#  連接到User數據庫connect('user', host='192.168.124.104', port=27017)

二、MongoEngine模型介紹

2.1、ODM模型介紹

from mongoengine import Document, StringFieldclass User(Document):    email = StringField(required=True)    first_name = StringField(max_length=50)    last_name = StringField(max_length=50)

2.2、常見數據類型

 2.3、數據類型通用參數

• db_field：文檔中得field/域/列名稱
• required：是否為必填項
• default：默認值
• unique：唯一性約束
• choices：可選擇得列表
• primary_key：是否為文檔得主鍵，默認為False

2.4、類屬性meta常見配置項

類屬性，其配置項為python得dict（字典）

from mongoengine import Document, StringFieldclass User(Document):    email = StringField(required=True)    first_name = StringField(max_length=50)    last_name = StringField(max_length=50)    meta = {    }

常見得配置項：

• db_alias：指定文檔所在得數據庫（邏輯庫）
• collection：指定文檔所在得集合
• ordering：指定文檔得默認排序規則
• indexes：指定文檔得索引規則

2.5、文檔得嵌套模型

學生信息數據字典

文檔得嵌套場景

情況一，數組-簡單數據類型：{'grades': [76, 51, 84]}

from mongoengine import Document, IntField, ListFieldclass Student(Document):    grade = ListField(IntField())

情況二，單個文檔：{'grade': {'course_name': '語文', 'score': 76}}

from mongoengine import Document, StringField, IntField, ListField, EmbeddedDocument, EmbeddedDocumentField#  自定義類型class CourseGrade(EmbeddedDocument):    course_name = StringField()    score = IntField()class Student(Document):    grade = EmbeddedDocumentField(CourseGrade)

情況三，數組-文檔：{'grades': [{'score': 76}, {'score': 51}]}

from mongoengine import Document, IntField, ListField, EmbeddedDocument, EmbeddedDocumentField#  自定義類型class CourseGrade(EmbeddedDocument):    score = IntField()class Student(Document):    grade = ListField(EmbeddedDocumentField(CourseGrade))

完整代碼：

from mongoengine import Document, connect, EnumField, StringField, IntField, ListField, EmbeddedDocument,     EmbeddedDocumentFieldfrom enum import Enum#  連接到User數據庫connect('user', host='192.168.124.104', port=27017)class SexEnum(Enum):    MAN = '男'    WOMAN = '女'class CourseGrade(EmbeddedDocument):    """成績信息（科目、老師、成績）-被嵌套得文檔"""    course_name = StringField(max_length=64, required=True, verbose_name='科目')    teacher = StringField(max_length=16, verbose_name='老師')    score = IntField(min_value=0, max_value=150, required=True, verbose_name='成績')    def __repr__(self):        return f"CourseGrade({self.course_name},{self.score})"    def __str__(self):        return self.__repr__()class Student(Document):    """學生信息"""    # verbose_name 自定義參數，用于顯示定義域得名稱    stu_no = IntField(required=True, unique=True, verbose_name='學號')    stu_name = StringField(required=True, max_length=16, verbose_name='姓名')    sex = EnumField(enum=SexEnum, verbose_name='性別')    class_name = StringField(max_length=10, verbose_name='班級')    address = StringField(max_length=255, verbose_name='家庭住址')    phone_no = StringField(max_length=11, verbose_name='電話號碼')    age = IntField(min_value=0, max_value=150, verbose_name='年齡')    grades = ListField(EmbeddedDocumentField(CourseGrade), verbose_name='成績數組')    meta = {        #  指定文檔得集合        'collection': 'students',        #  指定排序，可以指定多個域。例如：'age':根據年齡升序，'-age'：根據年齡降序        'ordering': ['-age']    }    def __repr__(self):        return f'Grade({self.stu_no}, {self.stu_name})'    def __str__(self):        return self.__repr__()class Grade(Document):    """學生成績"""    # verbose_name 自定義參數，用于顯示定義域得名稱    stu_no = IntField(required=True, verbose_name="學號")    stu_name = StringField(required=True, max_length=16, verbose_name='姓名')    sex = EnumField(enum=SexEnum, verbose_name='性別')    class_name = StringField(max_length=10, verbose_name='班級')    address = StringField(max_length=255, verbose_name='家庭住址')    phone_no = StringField(max_length=11, verbose_name='電話號碼')    age = IntField(min_value=0, max_value=150, verbose_name='年齡')    grade = EmbeddedDocumentField(CourseGrade, verbose_name='成績')    meta = {        # 指定文檔得集合        'collection': 'grades',        # 指定排序，可以指定多個域。例如：'age':根據年齡升序，'-age'：根據年齡降序        'ordering': ['-age']    }    def __repr__(self):        return f'Grade({self.stu_no}, {self.stu_name})'    def __str__(self):        return self.__repr__()

 三、添加數據

添加數據一般有兩種方式：

3.1、方式一

一般步驟：

• 第一步，構造ODM模型類對象：user=User(username='張三')
• 第二步，驗證數據：user.validate()
• 第三步，保存數據：user.save()

模型中得驗

• 內置得驗證器，如max_length, min_value
• 自定義驗證器

模型中自定義驗證方法示例代碼如下：

import refrom mongoengine import StringFieldfrom mongoengine.errors import ValidationErrordef phone_required(value):    pattern = r'^1[0-9][10]$'    if not re.search(pattern, value):        raise ValidationError('請輸入正確得手機號')phone_no = StringField(validation=phone_required)

方式一示例代碼：

import randomfrom model import Student, Grade, SexEnum, CourseGradeclass LearnMongoDBEngine(object):     def __init__(self, info):        self.info = info        print(self.info)     def add_one_student(self):        """新增一個學生信息"""        student = Student(            stu_no=random.randint(3000, 9999999),            stu_name=self.info['name'],            sex=random.choice([SexEnum.MAN, SexEnum.WOMAN]),            class_name='六年級三班',            address=self.info['address'],            phone_no=self.info['phone'],            age=random.randint(10, 15),            grades=[                CourseGrade(course_name='語文', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='數學', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='英語', teacher=self.info['teacher'], score=random.randint(1, 100)),            ]        )        print(student, student.grades)        result = student.save()        return resultif __name__ == '__main__':    info = {'name': '鐵扇公主', 'address': '北京市朝陽區', 'phone': '19121741234', 'teacher': '王老師'}     obj = LearnMongoDBEngine(info)    obj.add_one_student()

mongodb數據庫中插入得數據：

3.2、方式二：使用create()方法

User.objects.create(**kwargs)

示例代碼：

import randomfrom model import Student, Grade, SexEnum, CourseGradeclass LearnMongoDBEngine(object):    def __init__(self, info):        self.info = info        print(self.info)    def add_one_student(self):        """新增一個學生信息"""        result = Student.objects.create(            stu_no=random.randint(3000, 9999999),            stu_name=self.info['name'],            sex=random.choice([SexEnum.MAN, SexEnum.WOMAN]),            class_name='六年級三班',            address=self.info['address'],            phone_no=self.info['phone'],            age=random.randint(10, 15),            grades=[                CourseGrade(course_name='語文', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='數學', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='英語', teacher=self.info['teacher'], score=random.randint(1, 100)),            ]        )        # student = Student(        #     stu_no=random.randint(3000, 9999999),        #     stu_name=self.info['name'],        #     sex=random.choice([SexEnum.MAN, SexEnum.WOMAN]),        #     class_name='六年級三班',        #     address=self.info['address'],        #     phone_no=self.info['phone'],        #     age=random.randint(10, 15),        #     grades=[        #         CourseGrade(course_name='語文', teacher=self.info['teacher'], score=random.randint(1, 100)),        #         CourseGrade(course_name='數學', teacher=self.info['teacher'], score=random.randint(1, 100)),        #         CourseGrade(course_name='英語', teacher=self.info['teacher'], score=random.randint(1, 100)),        #     ]        # )        print(result, result.grades)        # result = student.save()        return resultif __name__ == '__main__':    info = {'name': '盧俊義', 'address': '上海市浦東新區', 'phone': '18721741234', 'teacher': '張老師'}    obj = LearnMongoDBEngine(info)    obj.add_one_student()

mongodb數據庫中插入得數據：

四、查詢數據

結果集QuerySet得獲?。?code>User.objects，User是模型對象

常用得查詢方法：

• all()：查詢所有文檔
• filter()：按照條件查詢
• count()：滿足條件得文檔數
• sum()/average()：求和/求平均數
• order_by()：排序
• .skip().limit()：分頁

4.1、單個文檔查詢

• first()：沒有文檔則返回None，User.objects.first()
• get(**kwargs)

多個文檔時，異常：MultipleObjectsReturned
沒有文檔時，異常：DoesNotExist
僅有一個文檔時：返回ODM對象

示例代碼：

from model import Studentclass LearnMongoDBEngine(object):    def get_one_student(self):        """查詢一個學生得信息"""        student_info = Student.objects.first()        print(student_info, student_info.id, student_info.stu_name, student_info.address)        return student_info    def get_all_student(self):        """查詢所有學生得信息"""        student_all_info = Student.objects.all()        print(student_all_info)        return student_all_info    def get_student_by_id(self, pk: str):        """根據學生得id查詢"""        student_info_id = Student.objects.get(id=pk)        print(student_info_id)        return student_info_idif __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.get_one_student()    obj.get_all_student()    obj.get_student_by_id('62dcd1f1a0da9e5521e73223')

運行結果：

4.2、條件查詢

1）比較運算符

 在MongoEngine中使用雙下劃線(__)分割。比如：age__gt=12，表示年齡大于12得學生信息。

2）MongoEngine中得字符串查詢   【i表示不區分大小寫】

3）多個條件組合查詢

• Q函數得使用：from mongoengine.queryset.visitor import Q
• 多個條件同時滿足：Student.objects.filter(Q(key1=value1) & Q(key2=value2))
• 多個條件部分滿足：Student.objects.filter(Q(key1=value1) | Q(key2=value2))

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def get_one_student(self):        """查詢一個學生得信息"""        student_info = Student.objects.first()        print(student_info, student_info.id, student_info.stu_name, student_info.address)        return student_info    def get_all_student(self):        """查詢所有學生得信息"""        student_all_info = Student.objects.all()        print(student_all_info)        return student_all_info    def get_student_by_id(self, pk: str):        """根據學生得id查詢"""        student_info_id = Student.objects.get(id=pk)        print(student_info_id)        return student_info_id    def get_student_1(self):        """獲取大于12歲得學生信息"""        result = Student.objects.filter(age__gt=12)        print(result)        return result    def get_student_2(self):        """獲取所有姓李得學生"""        result = Student.objects.filter(stu_name__startswith='李')        print(result)        return result    def get_student_3(self):        """查詢年齡在9~12之間（含）得學生信息"""        # SELECT * FROM school_student_info WHERE age BETWEEN 9 AND 12;        # db.students.find({'age': {'$gte': 9, '$lte': 12}})        result = Student.objects.filter(Q(age__gte=9) & Q(age__lte=12))        print(result)        return result    def get_student_4(self):        """查詢所有12歲以上得男生和9歲以下得女生"""        result = Student.objects.filter(Q(age__gt=12, sex=SexEnum.MAN) | Q(age__lt=9, sex=SexEnum.WOMAN))        print(result)        return result    def get_grade(self):        """查詢大于等于60分得學生成績信息"""        result = Student.objects.filter(grades__score__gte=80)  # 注意這兒寫法        print(result)        for i in result:            print(i.grades)        return resultif __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.get_one_student()    obj.get_student_1()    obj.get_student_2()    obj.get_student_3()    obj.get_student_4()    obj.get_grade()

運行結果：  【注意：打印信息是由model中__call__函數設置決定得】

4.3、聚合統計

• 滿足條件得文檔數：User.objects.count()，所有得結果集都可以使用
• 求和/平均數：User.objects.filter().sum(field) / User.objects.filter().average(field)

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def get_student_4(self):        """查詢所有12歲以上得男生和9歲以下得女生"""        result = Student.objects.filter(Q(age__gt=12, sex=SexEnum.MAN) | Q(age__lt=9, sex=SexEnum.WOMAN))        print(result)        return result     def get_student_5(self):        """查詢所有12歲以上得男生和9歲以下得女生總數"""        result = Student.objects.filter(Q(age__gt=12, sex=SexEnum.MAN) | Q(age__lt=9, sex=SexEnum.WOMAN)).count()        print(result)        return result     def get_man_sex(self):        """統計性別為男得總人數，并求出其平均年齡和總年齡"""        queryset = Student.objects.filter(sex='男')        print(queryset)        man_num_count = queryset.count()        print(man_num_count)        man_avg_age = queryset.average('age')        print(man_avg_age)        man_sum_age = queryset.sum('age')        print(man_sum_age)        return man_avg_age, man_sum_ageif __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.get_student_4()    obj.get_student_5()    obj.get_man_sex()

運行結果：

 4.4、排序

• -：倒敘排列
• (+)：正序排序，默認就是正序
• Student.objects().order_by('field1', '-field2')

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def get_max_min_age(self):        """獲取最大年齡和最小年齡得學生信息"""        queryset_min_age = Student.objects.order_by('age').first()        queryset_max_age = Student.objects.order_by('-age').first()        print(queryset_min_age, queryset_min_age.age)        print(queryset_max_age, queryset_max_age.age)         return '200 OK'if __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.get_max_min_age()

運行結果： 

 4.5、分頁處理

• 方式一，切片方式：User.objects.all()[10:15]
• 方式二，.skip().limit()：User.objects.skip(10).limit(5)

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def paginate(self, page: int = 1, page_size: int = 5):        """        分頁處理        :param page: 當前是第幾頁        :param page_size: 每頁有多少數據        :return:        """        #  方法一：切片        start = (page - 1) * page_size        end = start + page_size        queryset1 = Student.objects.all()[start:end]        print(queryset1)        #  方法二：skip().limit()        queryset2 = Student.objects.skip(start).limit(page_size)        print(queryset2)        return "200 OK"if __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.paginate(1, 6)    print("*" * 100)    obj.paginate(1, 3)    obj.paginate(2, 3)

運行結果：

 五、修改和刪除數據

5.1、修改數據

修改數據時一般先過濾數據，再修改

• 修改一條數據：User.objects.filter().update_one()
• 批量修改數據：User.objects.filter().update()

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def update_one(self):        """修改一條數據"""        queryset = Student.objects.filter(stu_no='2438197')        print(queryset)        result = queryset.update_one(stu_name='白龍馬', phone_no='16452412564')        # result = queryset.update_one(stu_name='白龍馬', unset__phone_no=True)        print(result)    def update_one_2(self):        """修改一條數據"""        queryset = Student.objects.filter(stu_no=3152784).first()        print(queryset)        if queryset:            queryset.stu_name = '沙和尚'            result = queryset.save()            print(result)            return "200 OK"        else:            return "error"    def update_many(self):        """將年齡10歲得學生年齡加一歲"""        queryset = Student.objects.filter(age=10)        print(queryset)        queryset.update(inc__age=1)        print(queryset)        return "200 OK"if __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.update_one()    obj.update_one_2()    obj.update_many()

運行結果：

5.2、刪除數據

User.objects.filter().delete()

from mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnumclass LearnMongoDBEngine(object):    def delete_data(self):        """刪除年齡大于13歲得學生"""        queryset_start = Student.objects.all()        print(f"刪除前學生總數量：{queryset_start.count()}")        queryset = Student.objects.filter(age__gt=13)        print(f'刪除得學生得數量：{queryset.count()}')        res = queryset.delete()        print(f"刪除得結果：{res}")        queryset_end = Student.objects.all()        print(f"刪除后剩余學生總數量：{queryset_end.count()}")if __name__ == '__main__':    obj = LearnMongoDBEngine()    obj.delete_data()

運行結果：

附錄：

main.py 

import randomfrom mongoengine.queryset.visitor import Qfrom model import Student, Grade, SexEnum, CourseGradeclass LearnMongoDBEngine(object):    def __init__(self, info):        self.info = info        print(self.info)    def add_one_student(self):        """新增一個學生信息"""        result = Student.objects.create(            stu_no=random.randint(3000, 9999999),            stu_name=self.info['name'],            sex=random.choice([SexEnum.MAN, SexEnum.WOMAN]),            class_name='六年級三班',            address=self.info['address'],            phone_no=self.info['phone'],            age=random.randint(10, 15),            grades=[                CourseGrade(course_name='語文', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='數學', teacher=self.info['teacher'], score=random.randint(1, 100)),                CourseGrade(course_name='英語', teacher=self.info['teacher'], score=random.randint(1, 100)),            ]        )        # student = Student(        #     stu_no=random.randint(3000, 9999999),        #     stu_name=self.info['name'],        #     sex=random.choice([SexEnum.MAN, SexEnum.WOMAN]),        #     class_name='六年級三班',        #     address=self.info['address'],        #     phone_no=self.info['phone'],        #     age=random.randint(10, 15),        #     grades=[        #         CourseGrade(course_name='語文', teacher=self.info['teacher'], score=random.randint(1, 100)),        #         CourseGrade(course_name='數學', teacher=self.info['teacher'], score=random.randint(1, 100)),        #         CourseGrade(course_name='英語', teacher=self.info['teacher'], score=random.randint(1, 100)),        #     ]        # )        print(result, result.grades)        # result = student.save()        return result    def get_one_student(self):        """查詢一個學生得信息"""        student_info = Student.objects.first()        print(student_info, student_info.id, student_info.stu_name, student_info.address)        return student_info    def get_all_student(self):        """查詢所有學生得信息"""        student_all_info = Student.objects.all()        print(student_all_info)        return student_all_info    def get_student_by_id(self, pk: str):        """根據學生得id查詢"""        student_info_id = Student.objects.get(id=pk)        print(student_info_id)        return student_info_id    def get_student_1(self):        """獲取大于12歲得學生信息"""        result = Student.objects.filter(age__gt=12)        print(result)        return result    def get_student_2(self):        """獲取所有姓李得學生"""        result = Student.objects.filter(stu_name__startswith='李')        print(result)        return result    def get_student_3(self):        """查詢年齡在9~12之間（含）得學生信息"""        # SELECT * FROM school_student_info WHERE age BETWEEN 9 AND 12;        # db.students.find({'age': {'$gte': 9, '$lte': 12}})        result = Student.objects.filter(Q(age__gte=9) & Q(age__lte=12))        print(result)        return result    def get_student_4(self):        """查詢所有12歲以上得男生和9歲以下得女生"""        result = Student.objects.filter(Q(age__gt=12, sex=SexEnum.MAN) | Q(age__lt=9, sex=SexEnum.WOMAN))        print(result)        return result    def get_student_5(self):        """查詢所有12歲以上得男生和9歲以下得女生總數"""        result = Student.objects.filter(Q(age__gt=12, sex=SexEnum.MAN) | Q(age__lt=9, sex=SexEnum.WOMAN)).count()        print(result)        return result    def get_man_sex(self):        """統計性別為男得總人數，并求出其平均年齡和總年齡"""        queryset = Student.objects.filter(sex='男')        print(queryset)        man_num_count = queryset.count()        print(man_num_count)        man_avg_age = queryset.average('age')        print(man_avg_age)        man_sum_age = queryset.sum('age')        print(man_sum_age)        return man_avg_age, man_sum_age    def get_grade(self):        """查詢大于等于60分得學生成績信息"""        result = Student.objects.filter(grades__score__gte=80)  # 注意這兒寫法        print(result)        for i in result:            print(i.grades)        return result    def get_max_min_age(self):        """獲取最大年齡和最小年齡得學生信息"""        queryset_min_age = Student.objects.order_by('age').first()        queryset_max_age = Student.objects.order_by('-age').first()        print(queryset_min_age, queryset_min_age.age)        print(queryset_max_age, queryset_max_age.age)        return '200 OK'    def paginate(self, page: int = 1, page_size: int = 5):        """        分頁處理        :param page: 當前是第幾頁        :param page_size: 每頁有多少數據        :return:        """        #  方法一：切片        start = (page - 1) * page_size        end = start + page_size        queryset1 = Student.objects.all()[start:end]        print(queryset1)        #  方法二：skip().limit()        queryset2 = Student.objects.skip(start).limit(page_size)        print(queryset2)        return "200 OK"    def update_one(self):        """修改一條數據"""        queryset = Student.objects.filter(stu_no='2438197')        print(queryset)        result = queryset.update_one(stu_name='白龍馬', phone_no='16452412564')        # result = queryset.update_one(stu_name='白龍馬', unset__phone_no=True)        print(result)    def update_one_2(self):        """修改一條數據"""        queryset = Student.objects.filter(stu_no=3152784).first()        print(queryset)        if queryset:            queryset.stu_name = '沙和尚'            result = queryset.save()            print(result)            return "200 OK"        else:            return "error"    def update_many(self):        """將年齡10歲得學生年齡加一歲"""        queryset = Student.objects.filter(age=10)        print(queryset)        queryset.update(inc__age=1)        print(queryset)        return "200 OK"    def delete_data(self):        """刪除年齡大于13歲得學生"""        queryset_start = Student.objects.all()        print(f"刪除前學生總數量：{queryset_start.count()}")        queryset = Student.objects.filter(age__gt=13)        print(f'刪除得學生得數量：{queryset.count()}')        res = queryset.delete()        print(f"刪除得結果：{res}")        queryset_end = Student.objects.all()        print(f"刪除后剩余學生總數量：{queryset_end.count()}")if __name__ == '__main__':    #  自我測試代碼    pass

model.py

from mongoengine import Document, connect, EnumField, StringField, IntField, ListField, EmbeddedDocument,     EmbeddedDocumentFieldfrom enum import Enum#  連接到User數據庫connect('user', host='192.168.124.104', port=27017)class SexEnum(Enum):    MAN = '男'    WOMAN = '女'class CourseGrade(EmbeddedDocument):    """成績信息（科目、老師、成績）-被嵌套得文檔"""    course_name = StringField(max_length=64, required=True, verbose_name='科目')    teacher = StringField(max_length=16, verbose_name='老師')    score = IntField(min_value=0, max_value=150, required=True, verbose_name='成績')    def __repr__(self):        return f"CourseGrade({self.course_name},{self.score})"    def __str__(self):        return self.__repr__()class Student(Document):    """學生信息"""    # verbose_name 自定義參數，用于顯示定義域得名稱    stu_no = IntField(required=True, unique=True, verbose_name='學號')    stu_name = StringField(required=True, max_length=16, verbose_name='姓名')    sex = EnumField(enum=SexEnum, verbose_name='性別')    class_name = StringField(max_length=10, verbose_name='班級')    address = StringField(max_length=255, verbose_name='家庭住址')    phone_no = StringField(max_length=11, verbose_name='電話號碼')    age = IntField(min_value=0, max_value=150, verbose_name='年齡')    grades = ListField(EmbeddedDocumentField(CourseGrade), verbose_name='成績數組')    meta = {        #  指定文檔得集合        'collection': 'students',        #  指定排序，可以指定多個域。例如：'age':根據年齡升序，'-age'：根據年齡降序        'ordering': ['-age'],        'strict': False  # 設置非嚴格校驗字段則不需要吧所有字段都聲明    }    def __repr__(self):        return f'Grade({self.stu_no}, {self.stu_name})'    def __str__(self):        return self.__repr__()class Grade(Document):    """學生成績"""    # verbose_name 自定義參數，用于顯示定義域得名稱    stu_no = IntField(required=True, verbose_name="學號")    stu_name = StringField(required=True, max_length=16, verbose_name='姓名')    sex = EnumField(enum=SexEnum, verbose_name='性別')    class_name = StringField(max_length=10, verbose_name='班級')    address = StringField(max_length=255, verbose_name='家庭住址')    phone_no = StringField(max_length=11, verbose_name='電話號碼')    age = IntField(min_value=0, max_value=150, verbose_name='年齡')    grades = EmbeddedDocumentField(CourseGrade, verbose_name='成績')    meta = {        # 指定文檔得集合        'collection': 'grades',        # 指定排序，可以指定多個域。例如：'age':根據年齡升序，'-age'：根據年齡降序        'ordering': ['-age']    }    def __repr__(self):        return f'Grade({self.stu_no}, {self.stu_name})'    def __str__(self):        return self.__repr__()

官方文檔：
 https://docs.mongoengine.org/guide/querying.html

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