Github URL: https://github.com/episyche/CRUD_Operations_On_MongoDB_Using_Mongoengine.git

Introduction:

MongoEngine is a Python Object-Document Mapping (ODM) library for working with MongoDB, a NoSQL database. It provides a high-level, intuitive way to interact with MongoDB, allowing developers to work with data in a more Pythonic and object-oriented manner.

MongoEngine is a convenient choice for Python developers looking to interact with MongoDB, especially in web development scenarios. It simplifies working with MongoDB by providing a more Python-friendly interface for data modelling and manipulation.

Prerequisites:

MongoDB Atlas account with Database instance/server

Basics of Flask

Flow Diagram:

Steps:

Installation:

Install MongoEngine Python Library. For a reference visit this website http://docs.mongoengine.org/tutorial.html#getting-started

pip install mongoengine

Initialise the MongoDB using the connection string

from mongoengine import *

connect("test_db_1", 
host="mongodb+srv://test-user:<password>@test-db.pfhwpga.mongodb.net/?retryWrites=true&w=majority")

Step 1: Define the structure of a table

class StudentList(Document):
    meta = {"collection": "student_list"}
    Roll_no = SequenceField(required=True)
    name = StringField(required=True)
    email = EmailField(required=True)

Using the ODM, we define the structure of the table before adding data to the database.

meta = {"collection": "student_list"} this meta statement defines the name of the table.

SequenceField NoSQL database won’t create a unique integer field like SQL Database ID; instead, it creates a unique UUID string to label every document present in the collection. If you want to create unique integer fields, MongoEngine by default provides a function.

When a field type is set to SequenceField, Unique increment integer fields are created, like in SQL.

Step 2: Create data

def createData():
    student_instance = StudentList(name="Tristan", email="tristan@gmail.com")
    student_instance.save()
    student_instance = StudentList(name="Sirena Fletcher", email="sirena@gmail.com")
    student_instance.save()
    student_instance = StudentList(name="Hazel Presley", email="hazel@gmail.com")
    student_instance.save()
    student_instance = StudentList(name="Kennard Fitzgerald", email="kennard@gmail.com")
    student_instance.save()
    student_instance = StudentList(name="Belinda Miles", email="belinda@gmail.com")
    student_instance.save()

If the database is empty, when the data is added for the first time, this method can be used.

def createDataWithoutDuplicate():
    student_instance = StudentList.objects.filter(email="tristan@gmail.com").first()
    if student_instance != None:
        student_instance.email = "tristan@yahoo.com"
        student_instance.save()
    Else:
        student_instance = StudentList(name="Tristan", email="tristan@gmail.com")
        student_instance.save()

To validate data already exists in the DB, you can use the above code to first check if an entry is present with a unique key. If present, update the existing entry or create a new entry.

Step 3: Update data


def  updateData():
    student_instance = StudentList.objects.filter(email="tristan@gmail.com").first()
    if student_instance != None:
        student_instance.email = "tristan@yahoo.com"
        student_instance.save()
    Else:
        print("Entry not found!")

To update an existing entry first, check whether the entry is available in the DB. If the entry exists, update the entry using the above code.

If the entry is present, we should throw a " data not available error message since it’s an update operation

Step 4: Retrieve data

Retrieve group of entries:

def getBulkData():
    student_instance = StudentList.objects.filter(location="india")
    For item in student_instance:
        print(item.email)

To retrieve bulk data from the database, you can use the above code

Step 5: Delete data

def deleteData():
    student_instance = StudentList.objects.filter(email="tristan@yahoo.com").first()
    if student_instance != None:
        student_instance.delete()
    Else:
        print("Entry not found!")

Result:

Using the above-given code, you can perform the CRUD operation on MongoDB using the Mongoengine library.

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