gui_main.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
import sys
from PyQt5.QtWidgets import (QWidget, QPushButton, QHBoxLayout, QVBoxLayout, QApplication)
class Example(QWidget):
    
    def __init__(self):
        super().__init__()
        self.initUI()
        
    def initUI(self):
        okButton = QPushButton("OK")
        cancelButton = QPushButton("Cancel")
        hbox = QHBoxLayout()
        hbox.addStretch(1)
        hbox.addWidget(okButton)
        hbox.addWidget(cancelButton)
        vbox = QVBoxLayout()
        vbox.addStretch(1)
        vbox.addLayout(hbox)
        
        self.setLayout(vbox)    
        
        self.setGeometry(300, 300, 300, 150)
        self.setWindowTitle('Buttons')    
        self.show()
         
if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())