How to change the position of labels, line edits, etc relative to the window size?

Question

I am creating a GUI app. All the windows in the app contain line edits, buttons, etc. I want the position of those to change relative to the window size, while the application is in use. The position of those should change if the user maximizes or alters the window size.

The code is as follows:

from PyQt5 import QtCore, QtGui, QtWidgets

class MainWindow(object):

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(1125, 969)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(350, 330, 361, 81))
        font = QtGui.QFont()
        font.setPointSize(24)
        font.setBold(True)
        font.setWeight(75)
        self.label.setFont(font)
        self.label.setObjectName("label")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(470, 510, 75, 51))
        self.pushButton.setObjectName("pushButton")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 1125, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")

        MainWindow.setStatusBar(self.statusbar)
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "Window"))
        self.label.setText(_translate("MainWindow", " Manager"))
        self.pushButton.setText(_translate("MainWindow", "Lets Start!"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    main_window = QtWidgets.QMainWindow()
    ui = MainWindow()
    ui.setupUi(main_window)
    main_window.show()
    sys.exit(app.exec_())

Answer 1

Since you are using Qt Designer I will offer a solution using that tool, for this you can use the following scheme:

QMainWindow
└── QHBoxLayout
    ├── QSpacerItem
    ├── QVBoxLayout
    │   ├── QSpacerItem
    │   ├── QLabel
    │   ├── QPushButton
    │   └── QSpacerItem
    └── QSpacerItem

Getting the following .ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>424</width>
    <height>179</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QHBoxLayout" name="horizontalLayout">
    <item>
     <spacer name="horizontalSpacer">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
        <width>129</width>
        <height>20</height>
       </size>
      </property>
     </spacer>
    </item>
    <item>
     <layout class="QVBoxLayout" name="verticalLayout">
      <item>
       <spacer name="verticalSpacer">
        <property name="orientation">
         <enum>Qt::Vertical</enum>
        </property>
        <property name="sizeHint" stdset="0">
         <size>
          <width>128</width>
          <height>13</height>
         </size>
        </property>
       </spacer>
      </item>
      <item>
       <widget class="QLabel" name="label">
        <property name="font">
         <font>
          <pointsize>24</pointsize>
          <weight>75</weight>
          <bold>true</bold>
         </font>
        </property>
        <property name="text">
         <string>Manager</string>
        </property>
        <property name="alignment">
         <set>Qt::AlignCenter</set>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QPushButton" name="pushButton">
        <property name="text">
         <string>Lets Start!</string>
        </property>
       </widget>
      </item>
      <item>
       <spacer name="verticalSpacer_2">
        <property name="orientation">
         <enum>Qt::Vertical</enum>
        </property>
        <property name="sizeHint" stdset="0">
         <size>
          <width>128</width>
          <height>13</height>
         </size>
        </property>
       </spacer>
      </item>
     </layout>
    </item>
    <item>
     <spacer name="horizontalSpacer_2">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <property name="sizeHint" stdset="0">
       <size>
        <width>128</width>
        <height>20</height>
       </size>
      </property>
     </spacer>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>424</width>
     <height>24</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

and then convert it to .py with pyuic.