Asynchronous context manager

Question

I have an asynchronous API which I\'m using to connect and send mail to an SMTP server which has some setup and tear down to it. So it fits nicely into using a context

Answer 1

In Python 3.7, you'll be able to write:

from contextlib import asynccontextmanager

@asynccontextmanager
async def smtp_connection():
    client = SMTPAsync()
    ...

    try:
        await client.connect(smtp_url, smtp_port)
        await client.starttls()
        await client.login(smtp_username, smtp_password)
        yield client
    finally:
        await client.quit()

Until 3.7 comes out, you can use the async_generator package for this. On 3.6, you can write:

# This import changed, everything else is the same
from async_generator import asynccontextmanager

@asynccontextmanager
async def smtp_connection():
    client = SMTPAsync()
    ...

    try:
        await client.connect(smtp_url, smtp_port)
        await client.starttls()
        await client.login(smtp_username, smtp_password)
        yield client
    finally:
        await client.quit()

And if you want to work all the way back to 3.5, you can write:

# This import changed again:
from async_generator import asynccontextmanager, async_generator, yield_

@asynccontextmanager
@async_generator      # <-- added this
async def smtp_connection():
    client = SMTPAsync()
    ...

    try:
        await client.connect(smtp_url, smtp_port)
        await client.starttls()
        await client.login(smtp_username, smtp_password)
        await yield_(client)    # <-- this line changed
    finally:
        await client.quit()