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Using MONGO DB IN PYTHON

Upcoming TEST 1: Mar 11, 2024 Monday 40 Questions: MCQ / 60 MINUTES

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https://www.mongodb.com/languages/python⁠

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Let’s start by installing MONGODB

and

MONGO DB Compass

https://www.mongodb.com/try/download/shell⁠

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PYTHON MONGO Checklist:

Checklist for Creating a Colors Database in MongoDB using Python:

Install MongoDB:

Download and install MongoDB from the official website
`https://www.mongodb.com/try/download/community`⁠

*** Choose the Option to install MONGOD as a service.

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Start the MongoDB server by running the command mongod in a terminal or command prompt.

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Using Visual Studio code to get this application going:

START VSC and make a Directory for your work:

Install PyMongo: Ensure that Python is installed on your system.

Install the PyMongo library using pip by running the command

pip install pymongo in a terminal or command prompt.

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Create a Python Script:

Open Visual Studion Code and create a new Python script (e.g., create_colors_database.py).

Connect to MongoDB:

Import the MongoClient class from the pymongo library.

Create a MongoClient instance to connect to the local MongoDB server.

Create a Database:

Add code to create a new MongoDB database using the MongoClient instance.

Verify Database Creation:

In order to work with `pymongo`, you must first ensure that you have the `pymongo` library installed. You can install it using the following pip command if it's not already installed:

```bash pip install pymongo ```

Now, let's take a step-by-step look at creating a

MongoClient instance, creating a new database, and verifying its creation in Python.

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1. Create a MongoClient Instance

First, you need to import `MongoClient` from `pymongo` and create an instance of `MongoClient` that will connect to your local MongoDB server.

Normally, MongoDB runs on port 27017 by default.

Here's how to establish the connection:

from pymongo import MongoClient

# Connect to the local MongoDB server client = MongoClient('localhost', 27017) ```

Alternatively, the connection string can be used:

```python # Connect to the local MongoDB server with connection string client = MongoClient('mongodb://localhost:27017/') ```

2. Create a Database

MongoDB creates databases and collections automatically for you if they do not exist already. Here's how you would create a new database:

```python # Create a new database called 'mydatabase' db = client['mydatabase'] ```

A database in MongoDB is not created until it gets content, so at this point, `mydatabase` is just a Python variable that will be mapped to a MongoDB database once content (like a collection) is added to it.

3. Verify Database Creation

Although databases in MongoDB are created lazily, you can still list all databases to verify whether or not your database name is registered as a part of the system.

Below is a simple code snippet to create a collection

and verify that the database has been created.

In MongoDB, a collection is analogous to a table in relational databases:

Assuming 'mydatabase' has no collections, let's create one to initialize the database

db.create_collection('mycollection')

# Now list all the databases in MongoDB database_list = client.list_database_names() print(database_list)

# Check if 'mydatabase' exists in the list of databases if 'mydatabase' in database_list: print("'mydatabase' exists.") else: print("'mydatabase' does not exist or has not been initialized with any data.") ```

In the above code, we tried to create a `collection` to ensure that the database is created.

Then we list all database names and check if our new database is in that list, even though the presence of a database in the list is not a definitive confirmation until at least one document is inserted into a collection.

Remember, a database in MongoDB stands up only upon insertion of the first document into a collection within that database (or, in some cases, when a collection is created explicitly). Thus, until you perform an actual insert operation, the new database may not show up in the server's database list.

In MongoDB, collections are analogous to tables in relational databases and can be created explicitly or implicitly.

When you add a document into a collection that does not exist, MongoDB automatically creates the collection.

Here's how to create a collection both implicitly and explicitly using PyMongo:

**Implicit Collection Creation**

When you insert a document into a collection that hasn't been created yet, MongoDB creates the collection automatically:

```python from pymongo import MongoClient

# Establishing a connection to the MongoDB server client = MongoClient('localhost', 27017)

# Selecting the database - it will be created if it does not exist db = client['mydatabase']

# Inserting a document - the collection 'mycollection' will be created implicitly result = db.mycollection.insert_one({'name': 'John', 'age': 30})

# You can now check that the 'mycollection' exists print('Collection created:', 'mycollection' in db.list_collection_names()) ```

**Explicit Collection Creation**

You can explicitly create a collection using the `create_collection` method. This is useful if you want to configure collection options, such as setting capped collections which limit the size or the number of documents a collection can have.

```python from pymongo import MongoClient

# Establishing a connection client = MongoClient('localhost', 27017)

# Selecting the database db = client['mydatabase']

# Explicitly creating a collection named 'mycollection' collection = db.create_collection('mycollection')

# Verifying that 'mycollection' exists print('Collection created:', 'mycollection' in db.list_collection_names()) ```

In the explicit creation, `create_collection` throws an error if the collection already exists unless you set the `strict` option to `False`.

Note that explicitly creating a collection without any options is not very common since MongoDB's philosophy embraces an implicit creation of collections and databases when they are first used.

To write to an existing "planetmars" database without re-creating it, you can follow these steps:

Connect to the MongoDB server and select the "planetmars" database using PyMongo.

from pymongo import MongoClient

# Connect to the local MongoDB server

client = MongoClient('localhost', 27017)

# Select the 'planetmars' database

db = client['planetmars']

Choose the collection within the "planetmars" database where you want to insert the records. If the collection already exists, you can directly insert the documents into it. If the collection does not exist, it will be created implicitly when you insert the first document.

# Choose the collection

collection = db['mycollection']

Insert the documents into the collection using the insert_one() or insert_many() method. The insert_one() method is used to insert a single document, while the insert_many() method is used to insert multiple documents at once.

# Insert a single document

result = collection.insert_one({'name': 'John', 'age': 30})

# Insert multiple documents

documents = [{'name': 'Alice', 'age': 25}, {'name': 'Bob', 'age': 35}]

result = collection.insert_many(documents)

Check the result of the insertion operation. The insert_one() and insert_many() methods return an instance of the InsertOneResult and InsertManyResult classes, respectively. You can access the inserted document's _id field from the result.

# Print the inserted document's _id

print(result.inserted_id)

By following these steps, you should be able to write to the existing "planetmars" database without re-creating it.It's important to remember that a collection is not physically created until you actually insert some data into it.

So, when you call `create_collection` without defining any options, you're essentially telling MongoDB to prepare to create the collection once a document is inserted unless you specify options that take effect immediately, like capped collections.

>>>>>

To acquire the "my_collection" collection without trying to re-create it, you can modify your code as follows:

from pymongo import MongoClient

# Connect to the local MongoDB server

client = MongoClient('localhost', 27017)

# Select the 'planetmars' database

db = client['planetmars']

# Choose the collection 'my_collection'

collection = db['my_collection']

# Now you can use the 'collection' object to perform operations on the collection

# For example, you can insert a document

result = collection.insert_one({'name': 'John', 'age': 30})

# Print the result

print(result)

# You can also check if the collection exists

if 'my_collection' in db.list_collection_names():

print("'my_collection' exists.")

else:

print("'my_collection' does not exist or has not been initialized with any data.")

By using the db['my_collection'] syntax, you can directly access the "my_collection" collection without trying to re-create it. This way, you can perform operations on the existing collection, such as inserting documents.

Please note that if the collection does not exist, it will be created implicitly when you insert the first document.

>>>>>

Making the Bears Database

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https://github.com/computationalknowledge/PythonicInformationSystem/blob/main/BearsDatabase⁠

Add Collection (Optional):

If desired, include code to create a collection within the created database. Finalize and Test:

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) instead.

Using MONGO DB IN PYTHON

PYTHON MONGO Checklist:

Checklist for Creating a Colors Database in MongoDB using Python:

Install MongoDB:

Download and install MongoDB from the official website https://www.mongodb.com/try/download/community⁠

Install PyMongo: Ensure that Python is installed on your system.

Create a Python Script:

Connect to MongoDB:

Import the MongoClient class from the pymongo library.

**1. Create a MongoClient Instance**

2. Create a Database

**3. Verify Database Creation**

Making the Bears Database

Download and install MongoDB from the official website
`https://www.mongodb.com/try/download/community`⁠

1. Create a MongoClient Instance

3. Verify Database Creation