RuntimeError：线程“ Thread-1”中没有当前事件循环。 -request_html，html.render（）

Question

I'm trying to render a HTML page in every 10 secs in Python with Requests-HTML module. For the first run it works perfectly, but after it crashes, with the error message below. My partial code is:

def get_data_from_page():
        session = HTMLSession()
        r = session.get('https://something.com/')
        threading.Timer(10.0, get_data_from_page).start()
        r.html.render()
    #code continues

def main():
    get_data_from_page()

if __name__ == '__main__':
    main()

Error message is:

Exception in thread Thread-1:

File "/home/david/.local/lib/python3.6/site-packages/requests_html.py", line 572, in render
        self.session.browser  # Automatycally create a event loop and browser
File "/home/david/.local/lib/python3.6/site-packages/requests_html.py", line 679, in browser
self.loop = asyncio.get_event_loop()
    File "/usr/lib/python3.6/asyncio/events.py", line 694, in get_event_loop
        return get_event_loop_policy().get_event_loop()
File "/usr/lib/python3.6/asyncio/events.py", line 602, in get_event_loop
    % threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'Thread-1'.

Answer 1

Instead of starting a timer (and thus a new thread) each time you want to do a request, it would probably be better to just start one thread that does the request every 10 seconds.

For example:

class RequestThread(Thread):
    def __init__(self):
        super().__init__()
        self.stop = Event()

    def run(self):
        while not self.stop.wait(10):
            session = HTMLSession()
            r = session.get('https://something.com/')
            r.html.render()   

    def stop(self):
         self.stop.set()

However, it seems requests_html is very thread unfriendly (it uses signals among other things). So you must run this in the main thread and create a thread for anything else you want to do. Something like this seems to work:

import requests_html
import time

def get_data_from_page():
    print(time.time())
    session = requests_html.HTMLSession()
    r = session.get('https://google.com')
    r.html.render()

while True:
    next_time = time.time() + 10
    get_data_from_page()

    wait_for = next_time - time.time()
    if wait_for > 0:
        time.sleep(wait_for)