#!/usr/bin/env python
import sys

from PySide2 import QtCore, QtGui, QtWidgets

from PySide2.QtUiTools import QUiLoader
from PySide2.QtWidgets import QApplication
from PySide2.QtCore import QFile


class MyWidget(QtCore.QObject):
    def __init__(self):
        QtCore.QObject.__init__(self)

        file = QFile("test.ui")
        file.open(QFile.ReadOnly)

        loader = QUiLoader()
        self.ui = loader.load(file)

        openAction = self.ui.findChild(QtWidgets.QAction, 'actionOpen')
        openAction.triggered.connect(self.func)

    @QtCore.Slot()
    def func(self):

        print("func has been called!")

app = QtWidgets.QApplication(sys.argv)
myWidget = MyWidget()
myWidget.ui.show()
sys.exit(app.exec_())