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Python PyMongo usage

Contents

• System environment
• Install pymongo
• Imports
• Initialize the connection
  • Parameters
  • Construct the URI
  • Connect to the MongoDB
  • Select the database
  • Select the collection
• Prepare the arguments
  • Example docs
    • One doc
    • Many doc
  • Queries
    • Select All Documents in a Collection
    • Specify Equality Condition
    • Specify Conditions Using Query Operators
    • Specify AND Conditions
    • Specify OR Conditions
    • Specify AND as well as OR Conditions
  • Update Operators
    • Set the value of a field to current date
    • Increment the value of the field by the specified amount
  • Aggregation Operators
    • Limit
    • Match
    • Projection
    • Sort
• Run the command
  • Insert Documents
    • Insert one document
    • Insert multiple documents
  • Number of documents in the collection
  • Find documents
  • Update Documents
    • Update one
    • Update many
    • Replace documents
  • Delete Documents
    • Delete one
    • Delete many
  • Aggregate operator
  • Print the cursor data
• Docker container
  • Dockerfile
  • Build the image
  • Configure
  • Run the container
• References

System environment

• Deployed MongoDB 4.4.3
• Python 3.9.1

Install pymongo

pip install pymongo==3.11.3

Imports

import os
from pprint import pprint

from pymongo import MongoClient

Initialize the connection

Parameters

MONGODB_USERNAME = os.environ.get("MONGODB_USERNAME")
MONGODB_PASSWORD = os.environ.get("MONGODB_PASSWORD")
MONGODB_HOST = os.environ.get("MONGODB_HOST")
MONGODB_DATABASE = os.environ.get("MONGODB_DATABASE")
MONGODB_COLLECTION = os.environ.get("MONGODB_COLLECTION")

Construct the URI

uri = f"mongodb://{MONGODB_USERNAME}:{MONGODB_PASSWORD}@{MONGODB_HOST}"

Connect to the MongoDB

connection = MongoClient(uri)

Select the database

db = connection[MONGODB_DATABASE]

Select the collection

collection = db[MONGODB_COLLECTION]

Prepare the arguments

Example docs

One doc

doc = {
    "item": "canvas",
    "qty": 100,
    "tags": ["cotton"],
    "size": {
	"h": 28,
	"w": 35.5,
	"uom": "cm"
    }
}

Many doc

docs = [
    {
        "item": "journal",
        "qty": 25,
        "size": {"h": 14, "w": 21, "uom": "cm"},
        "status": "A"
    },
    {
        "item": "notebook",
        "qty": 50,
        "size": {"h": 8.5, "w": 11, "uom": "in"},
        "status": "A"
    },
    {
        "item": "paper",
        "qty": 100,
        "size": {"h": 8.5, "w": 11, "uom": "in"},
        "status": "D"
    },
    {
        "item": "planner",
        "qty": 75,
        "size": {"h": 22.85, "w": 30, "uom": "cm"},
        "status": "D"
    },
    {
        "item": "postcard",
        "qty": 45,
        "size": {"h": 10, "w": 15.25, "uom": "cm"},
        "status": "A"
    }
]

Queries

Select All Documents in a Collection

query = {}

Specify Equality Condition

query = {"status": "D"}

Specify Conditions Using Query Operators

query = {"status": {"$in": ["A", "D"]}}

Specify AND Conditions

query = {"status": "A", "qty": {"$lt": 30}}

Specify OR Conditions

query = {"$or": [{"status": "A"}, {"qty": {"$lt": 30}}]}

Specify AND as well as OR Conditions

query = {
    "status": "A",
    "$or": [{"qty": {"$lt": 30}}, {"item": {"$regex": "^p"}}]
}

Update Operators

Set the value of a field to current date

update_operator = {
    "$currentDate": {
        "current_date_default": True,
        "current_date": {"$type": "date"},
        "current_timestamp": {"$type": "timestamp"}
    }
}

Increment the value of the field by the specified amount

update_operator = {
    "$inc": {
        "emptyField": 1,
        "a.a": 1,
    }
}

Aggregation Operators

pipeline = []

Limit

pipeline.append({
    "$limit": 100,
})

Match

pipeline.append({
    "$match": {"status": "A"}
})

Projection

pipeline.append({
    "$project": {"status": 1}
})

Sort

pipeline.append({
    "$sort": {"status": -1}
})

Run the command

Insert Documents

Insert one document

collection.insert_one(doc)

Insert multiple documents

collection.insert_many(docs)

Number of documents in the collection

collection.count_documents(query)

Find documents

cursor = collection.find(query)

Update Documents

Update one

collection.update_one(query, update_operator)

Update many

collection.update_many(query, update_operator)

Replace documents

collection.replace_one(query, doc)

Delete Documents

Delete one

collection.delete_one(query)

Delete many

collection.delete_many(query)

Aggregate operator

cursor = collection.aggregate(pipeline, allowDiskUse=True)

Print the cursor data

for doc in cursor:
     pprint(doc)

Docker container

Dockerfile

FROM python:3.9.1-buster
RUN pip install pymongo==3.11.3

Build the image

docker build -t python-pymongo-usage .

Configure

MONGODB_USERNAME=user
MONGODB_PASSWORD=topsecret
MONGODB_HOST=mongodb
MONGODB_DATABASE=newdb
MONGODB_COLLECTION=testcollection

Run the container

docker run --rm --link mongodb --env-file .env -it python-pymongo-usage python

References

1. https://docs.mongodb.com/manual/crud/