Async runtime

pyreqwest uses tokio Rust async runtime, similar to reqwest. By default, the library runs on a global single-threaded runtime chosen for simplicity and performance, which is sufficient for most use cases. If needed, you can use multithreaded runtime for a client via ClientBuilder.runtime_multithreaded(bool). It is also possible to enable multithreaded runtime globally via pyreqwest.runtime.runtime_multithreaded_default(bool). Multithreaded runtime may be beneficial if you have many concurrent requests and/or large responses to process. For more granular control over the runtime, you can use pyreqwest.runtime module to configure the runtime.

See benchmarking results showing single-threaded vs multi-threaded runtime performance.

Buffer protocol and zero-copying

Library makes extensive use of Python buffer protocol to avoid unnecessary copying of data. For example, request bodies are returned as pyreqwest.bytes.Bytes type. This is a bytes-like type that implements the buffer protocol. You can pass the data to other libraries and functions without copying via memoryview(Bytes). Converting to bytes/bytearray happens via bytes(Bytes) which copies the underlying buffer.

Many copy() operations provided by the library create a zero-copy view of the underlying data (e.g. Request.copy()), enabling efficient request retrying (when done e.g. via a middleware).

Library usually transfers ownership of its internal data structures between different functions calls, such as those sending requests or builders. Therefore, some instances become unusable after usage. For example, after calling Request.send(), the Request instance is no longer usable.

GIL releasing

Most operations release GIL, especially those doing any I/O operations. Also, various parsers release GIL such as JSON and text decoding.

Python 3.13+ free threading

Library supports Python 3.13+ free threading.

Following classes are thread-safe to use across multiple threads: Client, SyncClient, CookieStore. These do not require additional locking or synchronization. Multiple requests can be started by different threads concurrently.

Also, simple types and immutable types like Url, HeaderMap, Bytes, Mime, Cookie are thread-safe.

Builder classes are not thread-safe and should not be shared across threads. (For example ClientBuilder and SyncClientBuilder.) Multiple threads should not mutate the same builder object concurrently.

Also, request and response types are not thread-safe. (For example ConsumedRequest, Response, SyncConsumedRequest, SyncResponse.) Multiple threads should not read or write to the same request or response object concurrently.