Add an option to run an asyncio event loop automatically

[sametmax]

Experimenting with asyncio righ now is a pain. If I want just to use aiohttp to make a get request, I need to do:

import asyncio
import aiohttp

async def main():
    content = await asyncio.get('http://foo.com').content
    print(content)

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

Compare to doing the same with requests:

import requets
print(requests.get('http://foo.com').content)

I wish ptpython would have an --asyncio option which starts an event loop with the shell and run any command in it.

So my example with aiohttp would become:

$ ptpython --asyncio

Then:

import aiohttp
print(await asyncio.get('http://foo.com').content)

[jonathanslenders]

Hi @sametmax,

This is interesting and useful. (Sorry for the late reply!)

We can't make this the default for several reasons, but with the asyncio argument, that should definitely be possible.

One issue, regarding your last snippet that has await. Like it is at that point; that's not valid Python syntax. It's like a yield outside of a function. So, how do you feel about just wrapping that snippet in a function (in the background.) and calling it immediately? I don't see another option, but that could work.

Jonathan

[sametmax]

I talked with an iPython dev, he provided me with a %magic_command which open a bloc that does just that. Since ptpython doesn't have this concept, wrapping could work, but then you need to give it access to the variable of the previous scope, which mean you need to copy local(), pass it to the functions, and merge it to the new locals() dict.

[lorencarvalho]

@sametmax you can just do what https://github.com/dabeaz/curio does and have a run macro:

def run(coro):
    try:
        coro.send(None)
    except StopIteration as e:
        return e.value

Works for running a coroutine off an asyncio loop, very useful for tooling around a REPL:

osx ~ ❯❯❯ ptpython3
>>> import asyncio
  2 async def greeting(name):
  3     return "hello " + name
  4 def run(coro):
  5     try:
  6         coro.send(None)
  7     except StopIteration as e:
  8         return e.value
>>> run(greeting('loren'))
'hello loren'
>>>

[sametmax]

This will only run until the next yield/await, if you have several yields/awaits, you can simply use loop.run_until_complete, which I already have a shortcut for. But it's nowere as nice as having support for await inside the repl.

[Congee]

I really prefer ptpython over ipython for long. But I miss this ipython async/await feature so much. Which piece of code should I look into to implement this feature?

[Congee]

wait. does https://bugs.python.org/issue37028 mean we can use top level await in ptpython with python 3.8 without any change?