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Dear Ramalho,
I hope you are well. I'm writing to suggest an improvement for the “Type Hinting Asynchronous Objects” section in Chapter 21 for the next edition.
Enhancing Clarity with Examples
I believe that including additional examples in this section would significantly enhance understanding of how to properly use type hints for asynchronous objects. Here are some specific suggestions:
- Coroutines Example: A beneficial addition would be an example demonstrating type hints for coroutines. The following code showcases how to achieve this:
import asyncio
import socket
from collections.abc import AsyncGenerator, Generator, Coroutine, Callable
def get_ipv4_by_hostname(hostname: str) -> list[str]:
return list(
i[4][0]
for i in
socket.getaddrinfo(hostname, 0)
if i[0] is socket.AddressFamily.AF_INET
and i[1] is socket.SocketKind.SOCK_RAW
)
async def get_ipv4_by_hostname_async(hostname: str) -> list[str]:
return await asyncio.to_thread(get_ipv4_by_hostname, hostname)
async def print_domanin_ip(
domain: str,
get_ip: Callable[[str], Coroutine[None, None, list[str]]]) -> None:
ips = await get_ip(domain)
if ips:
for ip in ips:
print(f'{domain}: {ip}')
else:
print(f'{domain}: No IP found')
print('_' * 20)
async def main() -> None:
await print_domanin_ip('docker.com', get_ipv4_by_hostname_async)- AsyncGenerators Example: The official typing documentation provides an excellent and clear example for AsyncGenerators. Including a similar example in the book would be valuable:
async def echo_round() -> AsyncGenerator[int, float]:
sent = yield 0
while sent >= 0.0:
rounded = await round(sent)
sent = yield roundedI also guess that there might be a typo on the page 825, the image is provided below:
I think “to last” phrase should be removed because Coroutine is actually covariant on the third parameter.
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