MongoDB model with PyMongo

MongoDB

MongoDB is a popular open-source NoSQL database. NoSQL is a database technology to store and retrieve data which are not stored in database like the traditional tabular form of RDBMS. Scalability and superior performance are main beneifts of NoSQL databases over RDBMS. Mongodb uses JSON-style documents with dynamic schema to store data. Installation instructions of MongoDB will be found in it's documentation - Install MongoDB. 

PyMongo

PyMongo is a Python distribution containing tools for working with MongoDB, and is the recommended way to work with MongoDB from Python. To install PyMongo execute the command in terminal:

$ sudo pip install pymongo

Creating a model

I am going to create student model which will be used to  get, create, update, delete objects form database.

models.py

# -*- coding: utf-8 -*-
import pymongo


class Student(object):
    def __init__(self, registration, **kwargs):
        self._id = registration
        self.first_name = kwargs.get('first_name', '')
        self.last_name = kwargs.get('last_name', '')
        self.department = kwargs.get('department', '')
        self.session = kwargs.get('session', '')
        self.mobile = kwargs.get('mobile', '')

    def __str__(self):
        return self._id

    @staticmethod
    def get_db(dbname='student_db'):
        """
        make database connection and return a database instance
        """
        client = pymongo.MongoClient(host='localhost', port=27017)
        return client[dbname]

    @classmethod
    def get(cls, registration):
        """
        get student by registration number
        """
        db = Student.get_db()
        student_info = db.students.find_one({'_id': registration}, {'_id': 0})
        if student_info:
            student = Student(registration=registration, **student_info)
        else:
            student = Student(registration=registration)
        db.connection.close()
        return student

    @classmethod
    def get_all(cls):
        """
        get all students and return a list. for many student return a cursor instead.
        """
        db = Student.get_db()
        students = list(db.students.find())
        db.connection.close()
        return students

    def save(self):
        """
        save() method will create or update a document based on the _id attribute.
        """
        db = Student.get_db()
        db.students.save(self.__dict__)
        db.connection.close()

    @classmethod
    def remove_all(cls):
        """
        remove all documents for the collection.
        """
        db = Student.get_db()
        db.students.remove()
        students = list(db.students.find())
        db.connection.close()
        return students

    def remove(self):
        """
        remove a object from the collection.
        """
        db = Student.get_db()
        db.students.remove(self._id)
        db.connection.close()
        return self._id

Now this model can be used for CRUD operations.

>>>from models import Student
>>>student = Student.get('2008331041')
>>>student.first_name = "Salman"
>>>student.last_name = "Wahed"

>>>student.save()
>>>Student.get_all()

[{u'_id': u'2008331041',
  u'department': u'',
  u'first_name': u'Salman',
  u'last_name': u'Wahed',
  u'mobile': u'',
  u'session': u''}]