How to pass variable number of functions as arguments in Python

Question

I'd like to use method assesion.run(), which expects pointers to async functions. Number of functions differs, so I tried to make a list of functions and spread it in .run() arguments section. But when appending them to list, they immediately invoke. How to generate variable number of functions please?

from requests_html import AsyncHTMLSession
asession = AsyncHTMLSession()

urls = [
    'https://python.org/',
    'https://reddit.com/',
    'https://google.com/'
    ]

async def get_html(url):
    r = await asession.get(url)
    return r

functionList = []

for url in urls:
    functionList.append(get_html(url))

# results = asession.run(fn1, fn2, fn3, fn4, ...)
results = asession.run(*functionList)

for result in results:
    print(result.html.url)

Use either threading module or concurrent.futures model to build out a que. — Rashid 'Lee' Ibrahim
– Rashid 'Lee' Ibrahim, Commented Oct 27, 2021 at 21:11
sounds kind of like functionList.append(lambda url=url: get_html(url)) — Ry-
– Ry- ♦, Commented Oct 27, 2021 at 22:27
@Ry- wow, I was thinking about lambda but never thought about such application of it. Thanks! — pulsar777
– pulsar777, Commented Oct 28, 2021 at 6:51

Wai Ha Lee · Accepted Answer · 2021-10-28 14:31:30Z

1

You have to pass the async functions not the coruoutines. The run function calls the arguments to create the coruoutines and then create the tasks.

So when you pass the coroutines run invoke them instead of creating tasks.

The functions are called without argument, so you should use functools.partial to put in the argument:

from functools import partial


...
for url in urls:
    functionList.append(partial(get_html, url))

edited Oct 28, 2021 at 14:31

Wai Ha Lee

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answered Oct 28, 2021 at 2:45

nadapez

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