python qt : automatically resizing main window to fit content

Question

I have a main window which contains a main widget, to which a vertical layout is set. To the layout is added a QTableWidget only (for the moment).

When I start the application and call show on the main_window, only part of the QTableWidget is shown. I can extend the window manually to see it all, but I would like the window to have its size nicely adapted to the size of the QTableWidget.

Googling the question found a lot of posts on how to use resize to an arbitrary size, and call to resize(int) works fine, but this is not quite what I am asking

Lots of other posts are not explicit enough, e.g "use sizePolicy" or "use frameGeometry" or "use geometry" or "use sizeHint". I am sure all of them may be right, but an example on how to would be awesome.

Answer 1

You can do something like this, from within your MainWindow after placing all the elements you need in the layout:

self.setFixedSize(self.layout.sizeHint())

This will set the size of the MainWindow to the size of the layout, which is calculated using the size of widgets that are arranged in the layout.

Answer 2

I think overriding sizeHint() on the QTableWidget is the key:

import sys
from PyQt5.QtCore import QSize
from PyQt5.QtWidgets import QApplication, QMainWindow, QTableWidget

class Table(QTableWidget):
  def sizeHint(self):
    horizontal = self.horizontalHeader()
    vertical = self.verticalHeader()
    frame = self.frameWidth() * 2
    return QSize(horizontal.length() + vertical.width() + frame,
                 vertical.length() + horizontal.height() + frame)

class Main(QMainWindow):
  def __init__(self, parent=None):
    super(Main, self).__init__(parent)
    top = Table(3, 5, self)
    self.setCentralWidget(top)

if __name__ == '__main__':
  app = QApplication(sys.argv)
  main = Main()
  main.show()
  sys.exit(app.exec_())