[Python] Running pyppeteer in Flask gives 'ValueError: signal only works in main thread'

I am trying to integrate pyppeteer in a Flask app. I have a Python script that runs pyppeteer and takes a screenshot of a page. This is working fine if I run the script individually.

The problem is that the same script does not work when I run it in a Flash app.

I get the following error:

loop.run_until_complete(capture(url, 123123))
File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/
Versions/3.7/lib/python3.7/asyncio/base_events.py",
line 568, in run_until_complete
return future.result()
File "/App-path/flaskr/image_capture/__init__.py", line 6, in capture
browser = await launch()
File "/usr/local/lib/python3.7/site-packages/pyppeteer/launcher.py",
line 311, in launch
return await Launcher(options, **kwargs).launch()
File "/usr/local/lib/python3.7/site-packages/pyppeteer/launcher.py",
line 180, in launch
signal.signal(signal.SIGINT, _close_process)
File"/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/
Versions/3.7/lib/python3.7/signal.py", line 47, in signal
handler = _signal.signal(_enum_to_int(signalnum),
_enum_to_int(handler))
ValueError: signal only works in main thread.


The following code is used to capture a screenshot:

async def capture(code_url, codeId):
browser = await launch()
# print('Hello')
page = await browser.newPage()
await page.setContent('<div id="chart-container">ABCD</div>')
# print(await page.content())
await page.addScriptTag({'url':'''{code_url}'''})
await page.waitFor('.animateon')
await page.setViewport({
'width':await
page.evaluate('''document.documentElement.clientWidth''') ,
'height': await
page.evaluate('''document.documentElement.clientHeight'''),
'deviceScaleFactor': 10,
})
await page.screenshot({'path': '''./temp/screenshot/chart-
{codeId}.jpg''', 'type': 'jpeg'})
await browser.close()


The following code is where this method is called:

@app.route('/api/v1/screenshot', methods=["POST"])
def screenShot():
url = request.form['url']
loop.run_until_complete(capture(url, 123123))
return jsonify("Image captured Successfully!")


I am using asyncio loop to handle the async capture function. I have turned off the debugging mode.

Please suggest where I am going wrong.

Python version: 3.7

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