MongoClient

MongoDB is a fast database for storing data (documents) with no complex relational logic. It can be used through direct Python method calls.

This tutorial uses a local database on a Windows computer. It uses the Community release of MongoDB. The mongo.exe and mongod.exe programs must be run first.

Example program

Here we use the MongoClient object. We must pass a connection string to MongoClient—this is acquired by running mongo.exe.

from pymongo import MongoClient

# Run mongod.exe before running this program.
# Run mongo.exe to get the database connection string.
client = MongoClient("mongodb://127.0.0.1:27017")
# Specify the database name after the client object.
db = client.example_database

# Ensure everything is deleted from example collection.
# ... The name can anything to specify a collection.
db.example_collection.delete_many({})

db.example_collection.insert_many([
    {"type": "cat", "weight": 25, "color": "orange"},
    {"type": "dog", "weight": 35, "color": "black"},
    {"type": "cat", "weight": 10, "color": "black"}
])

# Find all things.
cursor = db.example_collection.find({})
print("FIND ALL")
for c in cursor:
    print(c)

# Find all animals that are black.
cursor = db.example_collection.find({"color": "black"})
print("FIND COLOR BLACK")
for c in cursor:
    print(c)

# Find all dogs.
cursor = db.example_collection.find({"type": "dog"})
print("FIND DOG")
for c in cursor:
   print(c)
FIND ALL
{'type': 'cat', 'weight': 25, 'color': 'orange',
 '_id': ObjectId('59ee4d922514973b084100a7')}
{'type': 'dog', 'weight': 35, 'color': 'black',
 '_id': ObjectId('59ee4d922514973b084100a8')}
{'type': 'cat', 'weight': 10, 'color': 'black',
 '_id': ObjectId('59ee4d922514973b084100a9')}
FIND COLOR BLACK
{'type': 'dog', 'weight': 35, 'color': 'black',
 '_id': ObjectId('59ee4d922514973b084100a8')}
{'type': 'cat', 'weight': 10, 'color': 'black',
 '_id': ObjectId('59ee4d922514973b084100a9')}
FIND DOG
{'type': 'dog', 'weight': 35, 'color': 'black',
 '_id': ObjectId('59ee4d922514973b084100a8')}

Notes, program

The program creates a database called example_database. It then creates a collection in the database called example_collection.

Notes, insert_many

We pass a dictionary argument to insert_many. Many rows (called documents) are added to the MongoDB collection.

In Python we can use a free and powerful NoSQL database. We use MongoClient to store documents in collections (which are inside databases).