import sys
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

class App(QMainWindow):

    def __init__(self):
        super().__init__()
        self.title = 'Surface Selector'
        self.left = 10
        self.top = 10
        self.width = 800
        self.height = 600
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.table_widget = MyTableWidget(self)
        self.setCentralWidget(self.table_widget)
        self.show()

class MyTableWidget(QWidget):

    def __init__(self, parent):
        super(QWidget, self).__init__(parent)
        self.layout = QVBoxLayout(self)

        # Initialize and add tabs
        self.tabs = QTabWidget()
        self.tab1 = QWidget()
        self.tab2 = QWidget()
        self.tabs.resize(800,600)
        self.tabs.addTab(self.tab1,"Load File")
        self.tabs.addTab(self.tab2,"Select Surface")

        # Page 1
        self.tab1.layout = QVBoxLayout(self)
        self.thing1 = QLabel(self)
        self.thing1.setText('Surface Selector')
        self.thing1.setAlignment(Qt.AlignCenter)
        self.button1 = QPushButton("Open file (.STP)")
        self.button1.clicked.connect(lambda: self.tabs.setCurrentIndex(1))
        self.tab1.layout.addWidget(self.thing1)
        self.tab1.layout.addWidget(self.button1)
        self.tab1.setLayout(self.tab1.layout)

        # Page 2
        self.tab2.layout = QVBoxLayout(self)
        self.thing2 = QLabel(self)
        pixmap2 = QPixmap('car1.png') # what I want is a 3D interactive viewer
        self.thing2.setPixmap(pixmap2)
        self.thing2.setAlignment(Qt.AlignCenter)
        self.button2 = QPushButton("Select Surface")
        self.button2.clicked.connect(self.output)
        self.tab2.layout.addWidget(self.thing2)
        self.tab2.layout.addWidget(self.button2)
        self.tab2.setLayout(self.tab2.layout)

        # Page 3
        # see car2.png...

        # Add tabs to widget
        self.layout.addWidget(self.tabs)
        self.setLayout(self.layout)

    def output(self):
        print('output a step file of selected surfaces...')


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())