Set scroll area initially moved - python-3.x

Question

I need to create a big widget inside a scroll area and initially set both sliders in the middle of the bar. The scroll bar does not work, the widgets are not well connected I think.
MRE:
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QWidget
import sys
class Diedrico(QWidget):
def __init__(self, parent=None):
super().__init__(parent)
# Draws stuff
class UiVentana(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super(UiVentana, self).__init__(parent)
ventana.resize(1500, 1015)
ventana.setFixedSize(1500, 1015)
self.widget_central = QtWidgets.QWidget(ventana)
scrol = QtWidgets.QScrollArea(self.widget_central)
scrol.setWidgetResizable(True)
scrol.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
scrol.setGeometry(QtCore.QRect(1010, 510, 470, 460))
self.Diedrico = Diedrico(scrol)
self.Diedrico.setGeometry(QtCore.QRect(0, 0, 1000, 1000))
# This widget should be big enough to use the scroll bar, but it does not work
ventana.setCentralWidget(self.widget_central)
ventana.show()
if __name__ == "__main__":
app = QtWidgets.QApplication([])
ventana = QtWidgets.QMainWindow()
ui = UiVentana()
sys.exit(app.exec_())

Answer 1

It seems that the problem comes from scrol.setWidgetResizable(True), which seems to resize the content... setting this to False worked for me.
Also, to center the scrollbar, there are a few options, like setting the value of the verticalScrollBar or using ensureVisible(x, y).
A working solution:
from PyQt5 import QtCore, QtWidgets
import sys
class UiVentana(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super(UiVentana, self).__init__(parent)
self.setupUi()
self.label.setGeometry(QtCore.QRect(10, 0, 282, 331))
self.label.setText("this is a long text\n" * 100)
self.scrollArea.verticalScrollBar().setValue(300)
def setupUi(self):
self.resize(800, 600)
self.centralwidget = QtWidgets.QWidget(self)
self.scrollArea = QtWidgets.QScrollArea(self.centralwidget)
self.scrollArea.setGeometry(QtCore.QRect(470, 330, 301, 211))
self.scrollArea.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
self.scrollArea.setWidgetResizable(False)
self.scrollAreaWidgetContents = QtWidgets.QWidget()
self.scrollAreaWidgetContents.setGeometry(QtCore.QRect(0, 0, 282, 10000))
self.label = QtWidgets.QLabel(self.scrollAreaWidgetContents)
self.scrollArea.setWidget(self.scrollAreaWidgetContents)
self.setCentralWidget(self.centralwidget)
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
ui = UiVentana()
ui.show()
sys.exit(app.exec_())