CRUD Operations in PyMongo

Create (Insert)

from pymongo import MongoClient
from datetime import datetime

client = MongoClient("mongodb://localhost:27017/")
db = client.mydb
users = db.users

# Insert one document
result = users.insert_one({
    "username": "john_doe",
    "email": "john@example.com",
    "created_at": datetime.utcnow()
})
print(f"Inserted ID: {result.inserted_id}")

# Insert many documents
result = users.insert_many([
    {"username": "jane_doe", "email": "jane@example.com"},
    {"username": "bob_smith", "email": "bob@example.com"},
])
print(f"Inserted IDs: {result.inserted_ids}")

Read (Query)

# Find one document
user = users.find_one({"username": "john_doe"})
print(user)

# Find by _id
from bson import ObjectId
user = users.find_one({"_id": ObjectId("507f1f77bcf86cd799439011")})

# Find multiple documents
cursor = users.find({"email": {"$regex": "@example.com"}})
for user in cursor:
    print(user)

# Find with projection (select specific fields)
cursor = users.find(
    {"username": "john_doe"},
    {"username": 1, "email": 1, "_id": 0}  # Include/exclude fields
)

# Count documents
count = users.count_documents({"active": True})

# Check if exists
exists = users.count_documents({"username": "john_doe"}, limit=1) > 0

Update

# Update one document
result = users.update_one(
    {"username": "john_doe"},  # Filter
    {"$set": {"email": "newemail@example.com"}}  # Update
)
print(f"Modified: {result.modified_count}")

# Update many documents
result = users.update_many(
    {"active": False},
    {"$set": {"active": True}}
)

# Upsert (insert if not exists)
result = users.update_one(
    {"username": "new_user"},
    {"$set": {"email": "new@example.com"}},
    upsert=True
)

# Replace entire document
users.replace_one(
    {"username": "john_doe"},
    {"username": "john_doe", "email": "john@new.com", "version": 2}
)

Delete

# Delete one document
result = users.delete_one({"username": "john_doe"})
print(f"Deleted: {result.deleted_count}")

# Delete many documents
result = users.delete_many({"active": False})

# Delete all documents (be careful!)
result = users.delete_many({})

Update Operators

# $set - Set field value
{"$set": {"name": "John"}}

# $unset - Remove field
{"$unset": {"temporary_field": ""}}

# $inc - Increment number
{"$inc": {"views": 1, "score": 10}}

# $push - Add to array
{"$push": {"tags": "python"}}

# $pull - Remove from array
{"$pull": {"tags": "obsolete"}}

# $addToSet - Add to array if not exists
{"$addToSet": {"tags": "unique"}}

# $rename - Rename field
{"$rename": {"old_name": "new_name"}}