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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add support for httpx and async transport","articleBody":"Add support for httpx for async transport. [An exemplar PR](https://github.com/googleapis/google-auth-library-python/pull/1908) to support this is available (it is currently closed to enable migration to the [Python mono-repo](https://github.com/googleapis/google-cloud-python)).\n\nBoth `aiohttp` and `httpx` are powerful libraries for making asynchronous HTTP requests in Python, but they serve slightly different purposes and have different design philosophies.\n\nHere is a breakdown of their differences, pros, cons, and when to use each, as provided by Gemini AI.\n\n---\n\n### 1. High-Level Overview\n\n*   **aiohttp:** The \"venerable\" choice. It has been the industry standard for asynchronous HTTP in Python for years. It is a full-featured networking library that provides both a **Client** and a **Server** framework.\n*   **httpx:** The \"modern\" choice. It was designed to be the spiritual successor to the famous `requests` library, but built for the modern `asyncio` era. Its biggest selling point is that it supports both **Synchronous** and **Asynchronous** APIs and has built-in support for **HTTP/2**.\n\n---\n\n### 2. Key Differences\n\n| Feature | aiohttp | httpx |\n| :--- | :--- | :--- |\n| **Sync Support** | No (Async only) | Yes (Sync and Async) |\n| **API Style** | Unique, explicit (requires `ClientSession`) | Very similar to `requests` |\n| **HTTP/2 Support** | No (supports HTTP/1.1 only) | Yes (Optional) |\n| **Web Server** | Yes (Built-in) | No (Client only) |\n| **Type Hinting** | Good | Excellent (Fully type-annotated) |\n| **Cookie/Session** | Strictly via `ClientSession` | Flexible (Top-level or Client) |\n\n---\n\n### 3. aiohttp\n\n#### Pros:\n*   **Performance:** Generally considered slightly faster and more efficient in high-concurrency benchmarks because it is highly optimized for `asyncio`.\n*   **Maturity:** It is battle-tested and has been used in production by major companies for nearly a decade.\n*   **All-in-one:** If you are building a web server and also need to make outgoing requests, you only need one library.\n*   **Control:** Offers lower-level control over connections and TCP parameters.\n\n#### Cons:\n*   **Async-Only:** You cannot use it in a synchronous script. This makes it difficult to share code between sync and async parts of a codebase.\n*   **Boilerplate:** It is more verbose. You *must* use a `ClientSession` context manager for almost everything.\n*   **No HTTP/2:** It currently does not support HTTP/2 for its client.\n\n---\n\n### 4. httpx\n\n#### Pros:\n*   **The \"Requests\" Feel:** If you know how to use `requests`, you know how to use `httpx`. The transition is almost seamless.\n*   **Sync \u0026 Async:** You can use `httpx.get()` for a quick script and `await client.get()` for an async app. This allows library authors to support both paradigms easily.\n*   **HTTP/2 Support:** This is a major advantage for modern web scraping and communicating with APIs that prioritize HTTP/2.\n*   **Strictness:** It has better defaults for things like timeouts (it enforces them by default, whereas `aiohttp` often doesn't).\n*   **WSGI/ASGI Support:** You can call your FastAPI or Flask app directly through `httpx` for testing without needing a running server.\n\n#### Cons:\n*   **Performance:** In some raw benchmarks, it is slightly slower than `aiohttp` (though this is rarely the bottleneck in real-world IO-bound applications).\n*   **Client Only:** It does not include a web server framework.\n\n---\n\n### 5. Code Comparison\n\n**aiohttp (Async only):**\n```python\nimport aiohttp\nimport asyncio\n\nasync def main():\n    async with aiohttp.ClientSession() as session:\n        async with session.get('https://example.com') as response:\n            print(response.status)\n            print(await response.text())\n\nasyncio.run(main())\n```\n\n**httpx (Async):**\n```python\nimport httpx\nimport asyncio\n\nasync def main():\n    async with httpx.AsyncClient() as client:\n        response = await client.get('https://example.com')\n        print(response.status_code)\n        print(response.text)\n\nasyncio.run(main())\n```\n\n---\n\n### 6. When to use which?\n\n#### Use **httpx** if:\n1.  **You want the best developer experience:** The API is cleaner and more intuitive.\n2.  **You need HTTP/2:** This is a non-negotiable requirement for some modern APIs.\n3.  **You are migrating from `requests`:** It will be much easier to port your code.\n4.  **You need both Sync and Async:** If you are writing a library or a CLI tool that needs to support both modes.\n5.  **You are using FastAPI:** `httpx` is the standard recommendation for testing and making external calls within FastAPI.\n\n#### Use **aiohttp** if:\n1.  **You are building a high-performance web server:** Using `aiohttp` as both the server and client keeps your stack unified.\n2.  **Raw speed is the googleapis/google-auth-library-python#1 priority:** If you are making millions of requests and every millisecond of overhead matters.\n3.  **Legacy codebases:** If you are working on an existing project that already uses `aiohttp`, there is rarely a compelling reason to switch.\n4.  **Complex TCP/Networking requirements:** If you need deep control over the underlying transport layer.\n\n### Summary\nFor **90% of new projects**, **`httpx`** is the recommended choice because of its flexibility, HTTP/2 support, and modern API. Use **`aiohttp`** only if you need its server-side capabilities or are working in a performance-critical, async-only environment where every drop of optimization counts.","author":{"url":"https://github.com/chalmerlowe","@type":"Person","name":"chalmerlowe"},"datePublished":"2025-12-30T12:40:01.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/15134/google-cloud-python/issues/15134"}