[BUG] Python3.7 ValueError: signal only works in main thread

[byehack]

Context:

• Playwright Version: 1.28
• Operating System: Linux
• Python version: 3.7
• Browser: Firefox
• Extra: ran on codespaces.

Code Snippet

from playwright.sync_api import sync_playwright

def my_thread():
    with sync_playwright() as pw:
        pass

threading.Thread(target=my_thread).start()

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/threading.py", line 926, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.7/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "-", line 958, in my_thread
  File "/home/vscode/.local/lib/python3.7/site-packages/playwright/sync_api/_context_manager.py", line 61, in __enter__
    asyncio.set_child_watcher(self._watcher)  # type: ignore
  File "/usr/local/lib/python3.7/asyncio/events.py", line 773, in set_child_watcher
    return get_event_loop_policy().set_child_watcher(watcher)
  File "/usr/local/lib/python3.7/asyncio/unix_events.py", line 1152, in set_child_watcher
    self._watcher.close()
  File "/usr/local/lib/python3.7/asyncio/unix_events.py", line 930, in close
    super().close()
  File "/usr/local/lib/python3.7/asyncio/unix_events.py", line 863, in close
    self.attach_loop(None)
  File "/usr/local/lib/python3.7/asyncio/unix_events.py", line 881, in attach_loop
    self._loop.remove_signal_handler(signal.SIGCHLD)
  File "/usr/local/lib/python3.7/asyncio/unix_events.py", line 147, in remove_signal_handler
    signal.signal(sig, handler)
  File "/usr/local/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

It is coming from this patch: #1213

[byehack]

relative intel/dffml@c1e8d85 intel/dffml@976a614

[byehack]

temporary solution is run once sync_playwright in main thread then use it in your threads. this is cause last asyncio loop need to configure and remove handlers from child watcher only in main thread.

import threading
from playwright.sync_api import sync_playwright

with sync_playwright() as pw: pass


def my_thread():
    with sync_playwright() as pw:
        ...


threading.Thread(target=my_thread).start()

[mxschmitt]

I apologize for the late reply. We dropped support for Python 3.7, so this seems not relevant anymore. Feel free to re-file if you are affected with 3.8+.