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Azure Cosmos Py

microsoft/azure-cosmos-py

| Azure Cosmos DB SDK for Python (NoSQL API). Use for document CRUD, queries, containers, and globally distributed data.

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Install

one command, takes just this skill from the repository
npx skills add https://github.com/microsoft/skills --skill azure-cosmos-py

What comes with it

21 382 bytes besides the instruction
references/partitioning.md
references/query-patterns.md

The instruction itself

23 sections, as written by the author

Azure Cosmos DB SDK for Python

Client library for Azure Cosmos DB NoSQL API — globally distributed, multi-model database.

Installation

pip install azure-cosmos azure-identity

Environment Variables

COSMOS_ENDPOINT=https://<account>.documents.azure.com:443/  # Required for all auth methods
COSMOS_DATABASE=mydb  # Required for all auth methods
COSMOS_CONTAINER=mycontainer  # Required for all auth methods
AZURE_TOKEN_CREDENTIALS=prod # Required only if DefaultAzureCredential is used in production

Authentication & Lifecycle

> 🔑 Two rules apply to every code sample below:

>

> 1. Prefer DefaultAzureCredential. It works locally (Azure CLI / VS Code / Developer CLI) and in Azure (managed identity, workload identity) with no code change. Avoid connection strings, account/API keys — they bypass Entra audit and rotation.

> - Local dev: DefaultAzureCredential works as-is.

> - Production: set AZURE_TOKEN_CREDENTIALS=prod (or AZURE_TOKEN_CREDENTIALS=<specific_credential>) to constrain the credential chain to production-safe credentials.

> 2. Wrap every client in a context manager so HTTP transports, sockets, and token caches are released deterministically:

> - Sync: with <Client>(...) as client:

> - Async: async with <Client>(...) as client: and async with DefaultAzureCredential() as credential: (from azure.identity.aio)

>

> Snippets may abbreviate this setup, but production code should always follow both rules.

import os
from azure.identity import DefaultAzureCredential, ManagedIdentityCredential
from azure.cosmos import CosmosClient

# Local dev: DefaultAzureCredential. Production: set AZURE_TOKEN_CREDENTIALS=prod or AZURE_TOKEN_CREDENTIALS=<specific_credential>
credential = DefaultAzureCredential(require_envvar=True)
# Or use a specific credential directly in production:
# See https://learn.microsoft.com/python/api/overview/azure/identity-readme?view=azure-python#credential-classes
# credential = ManagedIdentityCredential()

endpoint = "https://<account>.documents.azure.com:443/"

with CosmosClient(url=endpoint, credential=credential) as client:
    # Use client here (see following sections for operations)
    ...

Client Hierarchy

| Client | Purpose | Get From |

|--------|---------|----------|

| CosmosClient | Account-level operations | Direct instantiation |

| DatabaseProxy | Database operations | client.get_database_client() |

| ContainerProxy | Container/item operations | database.get_container_client() |

Core Workflow

Setup Database and Container

# Get or create database
database = client.create_database_if_not_exists(id="mydb")

# Get or create container with partition key
container = database.create_container_if_not_exists(
    id="mycontainer",
    partition_key=PartitionKey(path="/category")
)

# Get existing
database = client.get_database_client("mydb")
container = database.get_container_client("mycontainer")

Create Item

item = {
    "id": "item-001",           # Required: unique within partition
    "category": "electronics",   # Partition key value
    "name": "Laptop",
    "price": 999.99,
    "tags": ["computer", "portable"]
}

created = container.create_item(body=item)
print(f"Created: {created['id']}")

Read Item

# Read requires id AND partition key
item = container.read_item(
    item="item-001",
    partition_key="electronics"
)
print(f"Name: {item['name']}")

Update Item (Replace)

item = container.read_item(item="item-001", partition_key="electronics")
item["price"] = 899.99
item["on_sale"] = True

updated = container.replace_item(item=item["id"], body=item)

Upsert Item

# Create if not exists, replace if exists
item = {
    "id": "item-002",
    "category": "electronics",
    "name": "Tablet",
    "price": 499.99
}

result = container.upsert_item(body=item)

Delete Item

container.delete_item(
    item="item-001",
    partition_key="electronics"
)

Queries

Basic Query

# Query within a partition (efficient)
query = "SELECT * FROM c WHERE c.price < @max_price"
items = container.query_items(
    query=query,
    parameters=[{"name": "@max_price", "value": 500}],
    partition_key="electronics"
)

for item in items:
    print(f"{item['name']}: ${item['price']}")

Cross-Partition Query

# Cross-partition (more expensive, use sparingly)
query = "SELECT * FROM c WHERE c.price < @max_price"
items = container.query_items(
    query=query,
    parameters=[{"name": "@max_price", "value": 500}],
    enable_cross_partition_query=True
)

for item in items:
    print(item)

Query with Projection

query = "SELECT c.id, c.name, c.price FROM c WHERE c.category = @category"
items = container.query_items(
    query=query,
    parameters=[{"name": "@category", "value": "electronics"}],
    partition_key="electronics"
)

Read All Items

# Read all in a partition
items = container.read_all_items()  # Cross-partition
# Or with partition key
items = container.query_items(
    query="SELECT * FROM c",
    partition_key="electronics"
)

Partition Keys

Critical: Always include partition key for efficient operations.

from azure.cosmos import PartitionKey

# Single partition key
container = database.create_container_if_not_exists(
    id="orders",
    partition_key=PartitionKey(path="/customer_id")
)

# Hierarchical partition key (preview)
container = database.create_container_if_not_exists(
    id="events",
    partition_key=PartitionKey(path=["/tenant_id", "/user_id"])
)

Throughput

# Create container with provisioned throughput
container = database.create_container_if_not_exists(
    id="mycontainer",
    partition_key=PartitionKey(path="/pk"),
    offer_throughput=400  # RU/s
)

# Read current throughput
offer = container.read_offer()
print(f"Throughput: {offer.offer_throughput} RU/s")

# Update throughput
container.replace_throughput(throughput=1000)

Async Client

from azure.cosmos.aio import CosmosClient
from azure.identity.aio import DefaultAzureCredential

async def cosmos_operations():
    async with DefaultAzureCredential() as credential:
        async with CosmosClient(endpoint, credential=credential) as client:
            database = client.get_database_client("mydb")
            container = database.get_container_client("mycontainer")
            
            # Create
            await container.create_item(body={"id": "1", "pk": "test"})
            
            # Read
            item = await container.read_item(item="1", partition_key="test")
            
            # Query
            async for item in container.query_items(
                query="SELECT * FROM c",
                partition_key="test"
            ):
                print(item)

import asyncio
asyncio.run(cosmos_operations())

Error Handling

from azure.cosmos.exceptions import CosmosHttpResponseError

try:
    item = container.read_item(item="nonexistent", partition_key="pk")
except CosmosHttpResponseError as e:
    if e.status_code == 404:
        print("Item not found")
    elif e.status_code == 429:
        print(f"Rate limited. Retry after: {e.headers.get('x-ms-retry-after-ms')}ms")
    else:
        raise

Best Practices

  • Pick sync OR async and stay consistent. Do not mix azure.cosmos sync clients with azure.cosmos.aio async clients in the same call path. Choose one mode per module.
  • Always use context managers for clients and async credentials. Wrap every client in with CosmosClient(...) as client: (sync) or async with CosmosClient(...) as client: (async). For async DefaultAzureCredential from azure.identity.aio, also use async with credential: so tokens and transports are cleaned up.
  • Use DefaultAzureCredential for portable auth across local dev and Azure (avoid connection strings / API keys when possible).
  • Always specify partition key for point reads and queries
  • Use parameterized queries to prevent injection and improve caching
  • Avoid cross-partition queries when possible
  • Use upsert_item for idempotent writes
  • Use async client for high-throughput scenarios
  • Design partition key for even data distribution

10. Use read_item instead of query for single document retrieval

Reference Files

| File | Contents |

|------|----------|

| references/partitioning.md | Partition key strategies, hierarchical keys, hot partition detection and mitigation |

| references/query-patterns.md | Query optimization, aggregations, pagination, transactions, change feed |

| scripts/setup_cosmos_container.py | CLI tool for creating containers with partitioning, throughput, and indexing |

How to use it

Copy the folder

Take microsoft/azure-cosmos-py from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

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Install what it needs

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