So now you define the camera outside the worker, and pass it as an argument to the worker

cameraGui.py

@@ -16,6 +16,9 @@ from pyqtgraph_subclasses import CustomRectangularROI
 from zylaCameraWorker import CameraWorker
 from cameraParameterTree import CameraParameterTree
 
+from drivers.andorzyla import AndorZyla
+#from dummyAndor import AndorZyla
+
 import sys
 import numpy as np
 
@@ -189,8 +192,10 @@ class CameraGuiMainWindow(QMainWindow):
 if __name__ == "__main__":
     app = QtGui.QApplication([])
 
+    camera = AndorZyla(0)
+
     myGuiMainWindow = CameraGuiMainWindow()
-    cameraWorker = CameraWorker()
+    cameraWorker = CameraWorker(andor_camera=camera)
 
     cameraWorker.make_connections(myGuiMainWindow)
     myGuiMainWindow.make_connections(cameraWorker)

zylaCameraWorker.py

@@ -10,19 +10,16 @@ Created on Thu Apr  4 11:10:20 2019
 
 import numpy as np
 from PyQt5 import QtCore
-
-#from drivers.andorzyla import AndorZyla
-from dummyAndor import AndorZyla
 import threading
 
 
 class CameraWorker(QtCore.QObject):
     imageReadySignal = QtCore.pyqtSignal(np.ndarray, int)
 
-    def __init__(self):
+    def __init__(self, andor_camera):
         super().__init__()
 
-        self.cam = AndorZyla(0)
+        self.cam = andor_camera
         self.cam.Init()
         #self.cam.ExposureTime.setValue(0.1)
         print("camera worker initialized")
@@ -79,7 +76,6 @@ class CameraWorker(QtCore.QObject):
 
 
 
-
     @QtCore.pyqtSlot(int)
     def new_image_acquired(self, acq_index):
         self.imageReadySignal.emit(self.cam.acq_queue.get(), acq_index)