Client

A Client is what you keep open. Requests made with it share connections. Turn on persist_cookies and they share cookies too.

async with Client(
    base_url="https://api.example.com",
    headers={"Accept": "application/json"},
    timeout=(10.0, 3.0),
) as client:
    await client.get("/v1/items")

Defaults

Argument	Default	What it does
http_version	"3"	Try HTTP/3, then fall back to what the server supports.
tls_version	"default"	TLS 1.2 or newer.
keep_alive	True	Reuse the connection. False closes it when the response arrives.
timeout	(30.0, 0.0)	Seconds for the whole request, then a separate limit for connecting. 0 means no extra connect limit.
persist_cookies	False	Remember cookies for later requests on this client.
ip_version	"any"	"4" or "6" limits which addresses a hostname may use.
backend	"asyncio"	"threaded" runs the network work on a background thread.
raise_for_status	False	When True, a bad status raises before you see the response.

Connection limits, if you need them: 1024 connections in total, 64 to one host, 2048 kept idle. The pool of workers starts at 16 and grows to 512. Leave these alone unless you have a reason.

read_buffer_size is how much of a response is read at once. The default is 16 KiB. It must be greater than 1024.

Per request

The same names work on get, post, and the other methods. None uses the client value. That covers http_version, tls_version, tls_version_max, interface, unix_socket, ip_version, no_proxy, keep_alive, and timeout.

An empty string is a real override. interface="" does not pick a local address. unix_socket="" uses a normal connection. no_proxy="" sends every host through the proxy.

asyncio or threaded

"asyncio" is the default. "threaded" moves the network work onto a background thread. Use it when your event loop cannot watch RedC’s sockets. The methods you call are the same.