Whenever I try to create a Dialog which has an existant active parent Window, the placement of the Dialog on show (or exec_) is dependant upon the binding in question.

For example if have:

#simple_load.py

from __future__ import print_function
import sys

from Qt.QtWidgets import (
        QWidget, QApplication, QVBoxLayout, QPushButton, QDialog)
from Qt.QtCompat import loadUi


class Dialog(QDialog):
    def __init__(self, parent=None):
        super(Dialog, self).__init__(parent=parent)
        loadUi("untitled.ui", self)
        self.pushButton.clicked.connect(self.close)


class Widget(QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent=parent)
        self.layout = QVBoxLayout(self)
        self.btn = QPushButton('Click')
        self.btn.clicked.connect(self.clicked)
        self.layout.addWidget(self.btn)

    def clicked(self):
        dialog = Dialog(self)
        dialog.exec_()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = Widget()
    widget.show()
    app.exec_()

with untitled.ui as:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>Dialog</class>
 <widget class="QDialog" name="Dialog">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>199</width>
    <height>60</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Dialog</string>
  </property>
  <layout class="QVBoxLayout" name="verticalLayout">
   <item>
    <widget class="QLabel" name="label">
     <property name="text">
      <string>Message</string>
     </property>
    </widget>
   </item>
   <item>
    <widget class="QPushButton" name="pushButton">
     <property name="text">
      <string>OK</string>
     </property>
    </widget>
   </item>
  </layout>
 </widget>
 <resources/>
 <connections/>
</ui>

and I do

(py37env) D:\workspace\test>set QT_PREFERRED_BINDING=PySide2;PyQt5
(py37env) D:\workspace\test>python simple_load.py

I will get the second dialog at the top-left corner.

and if I do

(py37env) D:\workspace\test>set QT_PREFERRED_BINDING=PyQt5;PySide2
(py37env) D:\workspace\test>python simple_load.py

I will get the second dialog at the center of the parent window.

For python27 and PySide I get the second window wedged above the top left corner.

if I use the setup_ui function as in baseinstance1.py, I will get the second dialog in the middle of the screen regardless of the binding. This I can manipulate by overridiing showEvent and calling move.
Also that setup_ui does not make the child window be always on top of the parent window.

However, setup_ui and the override seem like just unnecessary inconvenient boiler plate in otherwise somewhat clean Qt.py and should probably be a part of the shim library. Am I wrong to expect consistent behaviour out of the box?