Lightweight Python asyncio HTTP/1.1 client.
Project description
lowhaio
A lightweight Python asyncio HTTP/1.1 client. No additional tasks are created; all code is in a single module; and other than the standard library only a single dependency is required, aiodnsresolver.
Connections are DNS-aware, in that they are only re-used if they match a current A record for the domain.
Installation
pip install lowhaio
Usage
The API is streaming-first: for both request and response bodies, asynchronous iterators are used.
import asyncio
from lowhaio import Pool
async def main():
request, close = Pool()
async def request_body():
yield b'a'
yield b'bc'
code, headers, response_body = await request(
b'POST', 'https://postman-echo.com/post',
headers=((b'content-length', b'3'), (b'content-type', b'text/plain'),),
body=request_body,
)
async for chunk in response_body:
print(chunk)
loop = asyncio.get_event_loop()
loop.run_until_complete(main())
However, there are helper functions streamed
and buffered
when this isn't required or possible.
import asyncio
from lowhaio import Pool, streamed, buffered
async def main():
request, close = Pool()
request_body = streamed(b'abc')
code, headers, response_body = await request(
b'POST', 'https://postman-echo.com/post',
headers=((b'content-length', b'3'), (b'content-type', b'text/plain'),),
body=request_body,
)
print(await buffered(response_body))
loop = asyncio.get_event_loop()
loop.run_until_complete(main())
Headers
The only header automatically added to requests is the host
header, which is the idna/punycode-encoded domain name from the requested URL.
Exceptions
Exceptions raised are subclasses of HttpError
. If a lower-level exception caused this, it is set in the __cause__
attribute of the HttpError
Exceptions before any data is sent are instances of HttpConnectionError
, and after data is sent, HttpDataError
. This is to make it possible to know if non-idempotent requests can be retried.
Scope
The scope of the core functions is restricted to:
- (TLS) connection opening, closing and pooling;
- passing and receiving HTTP headers and streaming bodies;
- decoding chunked responses;
- raising exceptions on timeouts.
This is to make the core behaviour useful to a reasonable range of uses, but to not include what can be added by layer(s) on top. Specifically not included:
- following redirects, implemented by lowhaio-redirect;
- retrying failed requests, implemented by lowhaio-retry;
- encoding chunked requests, implemented by lowhaio-chunked;
- authentication, such as AWS Signature Version 4 implemented by lowhaio-aws-sigv4, or AWS Signature Version 4 with unsigned payload implemented by lowhaio-aws-sigv4-unsigned-payload;
- compressing/decompressing requests/responses;
- cookies.
Project details
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