python requests async callback

Python Requests Async Callback

Python Requests is a popular library used for making HTTP requests in Python. It provides easy-to-use methods to send HTTP requests and handle responses. However, when making multiple requests and waiting for responses, it can become time-consuming to wait for each request to complete before moving on to the next one. That's where async callbacks come into play.

Async Callbacks with Requests

Async callbacks allow us to send multiple requests simultaneously and receive responses as they become available, without waiting for all requests to complete before moving on. With Python Requests, we can use the asyncio library to send requests asynchronously and handle responses using callbacks.

Here's an example of using async callbacks with Requests:

import asyncio
import requests

async def get_data_async(url):
    response = await loop.run_in_executor(None, requests.get, url)
    return response.json()

def handle_response(response):
    print(response)

async def main():
    urls = [
        "https://jsonplaceholder.typicode.com/todos/1",
        "https://jsonplaceholder.typicode.com/todos/2",
        "https://jsonplaceholder.typicode.com/todos/3"
    ]
    futures = [get_data_async(url) for url in urls]
    for future in asyncio.as_completed(futures):
        response = await future
        handle_response(response)

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

In this example, we define a function get_data_async(url) that sends a GET request to the specified URL and returns the response as a JSON object. We use the asyncio.run_in_executor() method to run requests.get() in a separate thread and wait for the response.

We define another function handle_response(response) that prints the response to the console. This function will be called for each response received.

In the main() function, we define a list of URLs to send requests to. We create a list of futures using the get_data_async() function for each URL. We then iterate over each future using asyncio.as_completed(), which returns a generator that yields futures as they complete. For each completed future, we await the result and pass it to handle_response().

Alternative Approach: aiohttp library

Another popular library for async HTTP requests in Python is aiohttp. It provides similar functionality to Requests, but with better support for async requests.

Here's an example of using aiohttp to send async requests:

import aiohttp
import asyncio

async def fetch(session, url):
    async with session.get(url) as response:
        return await response.json()

async def main():
    async with aiohttp.ClientSession() as session:
        urls = [
            "https://jsonplaceholder.typicode.com/todos/1",
            "https://jsonplaceholder.typicode.com/todos/2",
            "https://jsonplaceholder.typicode.com/todos/3"
        ]
        tasks = [asyncio.create_task(fetch(session, url)) for url in urls]
        responses = await asyncio.gather(*tasks)
        print(responses)

asyncio.run(main())

In this example, we define a function fetch(session, url) that sends a GET request to the specified URL using an aiohttp.ClientSession. We use the async with statement to ensure that the session is closed properly after the request is completed.

In the main() function, we create a list of URLs to send requests to. We create a list of tasks using the fetch() function for each URL. We use asyncio.gather() to wait for all tasks to complete and return their results as a list.

Both the Requests and aiohttp libraries provide simple and easy-to-use methods for sending HTTP requests in Python. Async callbacks allow us to send multiple requests simultaneously and handle responses as they become available, improving the performance and scalability of our applications.