I am creating a new thread to separate the UI interface from the data processing logic., but for reasons completely unfathomable to me, when I build and run my app , the app promptly crashes with the exception:
File "capnp/lib/capnp.pyx", line 2150, in capnp.lib.capnp._DynamicCapabilityClient._send
capnp.lib.capnp.KjException: src/kj/async.c++:53: failed: expected loop != nullptr; No event loop is running on this thread.
stack: 0x7f9bd4774489 0x7f9bd477845d 0x7f9bd4c0aacc 0x7f9bd49a81cb 0x7f9bd49a8207 0x7f9bd49a8304 0x7f9bd54d0341 0x7f9bd4edb93e 0x7f9bd4edba96 0x7f9bd4ec305e 0x7f9bd4ec43e9 0x7f9bd4eb0651 0x7f9bd54b5ad8 0x7f9bd5485844 0x55b92dc620c5 0x55b92dd55107
I'm not sure what in the build system could cause this runtime error，here is my code ,My best guess is some kind of arcane linking quirk, but I have no idea what or how to fix it.
import sys
import os
from PyQt5.QtCore import *
from PyQt5.QtGui import QGuiApplication
from cnc import Cnc
cnc = Cnc(os.path.join(os.getenv("HOME"), "cnc"), "192.168.7.98")
class workthread(QThread):
def __init__(self):
super(workthread, self).__init__()
def run(self):
self.cnc_axis_names = {axis.id: axis.name.absolute for axis in cnc.axes}
self.coors = {self.cnc_axis_names[id_]: coor for id_, coor in cnc.axes.coors().items()}
data = list(self.coors.values())
print(data)
self.sleep(1)
self.run()
self.exic_()
if __name__ == '__main__':
thread1 = workthread()
thread1.start()
app = QGuiApplication(sys.argv)
sys.exit(app.exec_())
Any advice on how to troubleshoot this is welcome.
I don't know what cnc is, but my guess is that it uses Cap'n Proto RPC. Cap'n Proto RPC uses a single-threaded event loop concurrency model, so RPC objects originally created on one thread cannot be manipulated on another thread.
In your program, you are creating the cnc object at startup, in the main thread. You then create a new thread and try to access the object from there. This won't work. You need to construct and use the object on a single thread.