Azure Functions Python Library

Warnings

• breaking The Python v2 programming model (used by `azure-functions` 2.0.0+) introduces significant breaking changes from v1. This shifts from using `function.json` files and a strict 'one function per folder' structure to a Python-first, decorator-based approach. Configuration for triggers and bindings is now directly within Python code.
  Fix: Rewrite function definitions using decorators (`@app.route`, `@app.timer_trigger`, etc.) in a `function_app.py` file or using blueprints. Remove individual `function.json` files. Refer to the official Azure Functions Python v2 programming model documentation for migration guidance.
• deprecated Azure Functions Runtime versions 2.x and 3.x are End-of-Life (EOL) and no longer supported. While apps on these runtimes may still function, they will not receive new features, security patches, or performance optimizations.
  Fix: Migrate your Function Apps to Azure Functions Runtime version 4.x as soon as possible for full support and access to the latest Python versions (3.10, 3.11, 3.12, 3.13 are supported by runtime 4.x). Ensure your Python code is compatible with the v2 programming model.
• gotcha Cold starts can significantly impact performance on the Consumption Plan. When a function app goes idle, Azure deallocates resources, leading to a delay (cold start) on the next invocation.
  Fix: To mitigate cold starts, consider using a Premium Plan (which keeps instances warm), scheduling periodic 'keep-alive' pings, or keeping your startup code lean by avoiding unnecessary library loads or connections.
• gotcha Default function timeouts on the Consumption Plan are 5 minutes and cannot be changed. Long-running tasks will be terminated.
  Fix: For longer execution times, use a Premium or Dedicated Plan. Alternatively, break down long tasks into smaller, parallelizable chunks, or offload heavy work to Durable Functions or other compute services.
• gotcha Repeatedly instantiating network clients (e.g., `HttpClient`, database connections) within a function's execution path can lead to `Socket Exception` errors due to resource exhaustion and inefficient connection management.
  Fix: Reuse client instances where possible. For Python, this often means creating clients outside the function handler (e.g., as global variables or in a singleton pattern) or utilizing connection pooling where available.
• gotcha Function App host names (which derive from the app name) have a maximum length of 32 characters. Longer names can lead to host ID collisions, especially when sharing a storage account, which can impede scaling and lease management.
  Fix: Ensure your Azure Function App names are 32 characters or less. Avoid sharing a single storage account across multiple Function Apps if possible.

Install

• pip install azure-functions Install core library

Imports

• func

  import azure.functions as func

  The recommended and standard alias for the Azure Functions library.
• FunctionApp

  app = func.FunctionApp()

  Initialize the FunctionApp object, the entry point for defining functions in the v2 programming model.
• HttpRequest

  req: func.HttpRequest

  Type hint for an HTTP request object.
• HttpResponse

  func.HttpResponse(...)

  Class for creating an HTTP response object.

Quickstart

This quickstart demonstrates a simple HTTP-triggered Azure Function using the Python v2 programming model. It shows how to define a function with the `@app.route` decorator, access request parameters (`HttpRequest`), and return an HTTP response (`HttpResponse`). This code is placed in a `function_app.py` file.

import azure.functions as func
import logging
import os

# Instantiate the FunctionApp object
app = func.FunctionApp()

# Define an HTTP trigger function using a decorator
@app.route(route="http_example", methods=["GET", "POST"])
def http_example(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')

    # Get name from query parameters or request body
    name = req.params.get('name')
    if not name:
        try:
            req_body = req.get_json()
        except ValueError:
            pass
        else:
            name = req_body.get('name')

    if name:
        return func.HttpResponse(f"Hello, {name}. This HTTP triggered function executed successfully.")
    else:
        return func.HttpResponse(
             "Please pass a name on the query string or in the request body for a personalized response.",
             status_code=200
        )