Pymongo: Learn how to integrate mongoDB with Python - Complete CRUD operations for handling mongoDB data using python

MongoDb is one of most popular NoSQL database utilized nowadays. It is so because it is very simple to install and top use, beyond there are several cloud services on cloud which provides a mongoDb instance to use.

In the other hand, python is a programming language typically adopted for big data applications because of the simple way it handles with computer memory allowing programs to have large numbers on memory using simple and native data types.

In this article it will be presented how to connect in a mongoDB serve using python, and how to perform all CRUD operations.

First it is necessary to install the pymongo module, which can be easily installed with pip tool, using the following instruction: python -m pip install pymongo

Once it is installed you my use the example code below, which imports the class MongoClient, and when instantiate a object of this class, parametrize with the connection string to create a link with mongo db server. Once it is done, you may access a specific database and a specific collection within this database. As you can see in the example below, the access of a database of a collection is done accessing then as normal attributes within the client object.

# python -m pip install pymongo
from pymongo import MongoClient
import datetime
client = MongoClient('mongodb://localhost:27017/')
#Acessing a especific database
db = client.company
#Acessing a especific collection
collection = db.employees

 

Once we have access to the collection object, this object that has methods to perform the CRUD operations. The first operation we are going to see this the .find_one() and .find(). The find_one, is quite simple to use. It basically returns the first object of an collection, and the returned object can be accessed directly. In the other hand, the find() method receives a parameter, which is the “query object”. The “query object” is very important, because it will be utilized in almost all methods. It is like the where clause in a SQL statement. It is a normal JSON object, which each object attribute is a criteria the document must match to return in the query. The find_all() method returns a list, and then objects from the list needs to be individually accessed to have access to its attributes.

print("### CRUD: Recovery")
print("### Find one ###")
document = collection.find_one()
print(document)
print("### Find  ###")
resultSet = collection.find({'name': 'Rafael'})
for document in resultSet:
    print(document)
print("### find all  ###")
resultSet = collection.find({})
for document in resultSet:
    print(document)

 

The next method we are going to study is the insert_one. It is quite simple, basically we have to pass a object as a method parameter, and it will be inserted int he respective collection. It is simple, because as MongoDB is NoSQL, it is almost error free operation (No matter the object structure, it will be inserted).

print("### CRUD: Create")
print("### .insert_one()  ###")
document = {
        "name": "Adrian",
        "lastName": "Tepes"
}
print("Collection document count BEFORE insert:", collection.count_documents({}))
insert_result = collection.insert_one(document)
print("Collection document count AFTER insert:", collection.count_documents({}))
id = insert_result.inserted_id
print("Generated id on insert:", id)

 

Next, the update or update_one method has two parameters: the query object, as we have utilized in the find method, and also a update object, which includes the attributes to be created or updated in objects that match the query object. It is interesting to observe that if object already have a certain attribute it will be overwritten, it it does not have it, it will be created.

print("### CRUD: Update")
print("### update: update_one or update_many  ###")
query = {"_id": id}
newValues = {"$set": {"updated_on": datetime.datetime.utcnow()}}
collection.update_one(query, newValues)
print("Updated object:", collection.find_one(query))
print("### update_many ###")
query = {"name": {"$ne": "Adrian"}} # != or <> => different than operator
newValues = {"$set": {"updated_on": datetime.datetime.utcnow()}}
collection.update_many(query, newValues)
resultSet = collection.find({})
for document in resultSet:
    print(document)

 

The last method we are going to see is the delete. The interface of this method is the same of .find() method. The main difference is that instead of just returning the objects that match the query, it will delete these objects from the respective collection?

print("### CRUD: Delete")
print("### Delete: .delete_one or .delete_many ###")
query = {"name": "Adrian"}
print("Collection document count BEFORE delete:", collection.count_documents({}))
collection.delete_many(query)
print("Collection document count AFTER delete:", collection.count_documents({}))
resultSet = collection.find({})
for document in resultSet:
    print(document)

 

So, do you want to execute this code in your on computer? You can download that in the link below?

 https://github.com/rafaelqg/code/blob/main/python_mongo_db_crud.py

This explanation is too abstract? You may see a practical hands on demonstration in this video?



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