aiofiles
Async file I/O library for Python's asyncio. Wraps standard Python file operations (open, read, write, close) in asyncio-compatible coroutines so they don't block the event loop. Essential for async Python applications (FastAPI, aiohttp, Starlette) that need to read/write files without freezing the event loop. Uses thread pool executors under the hood to offload blocking file operations.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Local file library — no network surface. Access controlled by OS permissions. No secrets needed. Minimal attack surface.
⚡ Reliability
Best When
You're building async Python applications (FastAPI, aiohttp, Starlette) that need to read/write files without blocking the event loop.
Avoid When
You're writing synchronous Python code or need OS-native async file I/O performance — aiofiles uses thread pools, not true kernel async IO.
Use Cases
- • Read configuration files, templates, or data files in async FastAPI/aiohttp handlers without blocking the event loop
- • Write log files, output artifacts, or processed data from async agent pipelines
- • Stream large files asynchronously in chunks to avoid loading entire file into memory in async web servers
- • Process uploaded files in async web handlers (read, transform, write) without blocking concurrent requests
- • Implement async file-based caching or persistence layers in asyncio-based agent systems
Not For
- • Sync Python code — use standard open()/pathlib for synchronous applications
- • High-performance file I/O at scale — use memory-mapped files or async OS-native io_uring for extreme performance
- • Directory watching/monitoring — use watchfiles or watchdog for file system events
Interface
Authentication
No authentication — local file system library. File access controlled by OS file permissions.
Pricing
Fully free, open source, Apache 2.0 licensed.
Agent Metadata
Known Gotchas
- ⚠ aiofiles uses thread pool executors under the hood — not true kernel async IO; for extreme file I/O performance, consider io_uring via alternative libraries
- ⚠ Must use 'async with aiofiles.open()' — forgetting async context manager will raise errors; file handle is an async context manager, not a regular one
- ⚠ File mode strings are the same as standard open() — agents must specify 'rb' for binary read, 'w' for text write, etc., same rules apply
- ⚠ aiofiles doesn't support all file modes and operations — some less common operations (mmap, fileno) are not wrapped; fall back to sync code for those
- ⚠ Concurrent writes to the same file from multiple coroutines will interleave — use asyncio.Lock() around file write operations if multiple coroutines write the same file
- ⚠ Thread pool size defaults to the executor's default — very high file I/O concurrency may exhaust the thread pool; configure loop.set_default_executor() for tuning
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for aiofiles.
Scores are editorial opinions as of 2026-03-06.