如何在pyqt5中获取当前窗口大小？

QWidget::resizeEvent(QResizeEvent *事件)

可以在子类中重写此事件处理程序以接收在 event 参数中传递的小部件调整大小事件。当调用 resizeEvent() 时，小部件已经有了新的几何图形。旧尺寸可通过 QResizeEvent::oldSize() 获得。

作为一种选择

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


class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(950, 640)
        self.pushButton = QtWidgets.QPushButton(Form)
        self.pushButton.setGeometry(QtCore.QRect(200, 510, 541, 121))
        self.pushButton.setObjectName("pushButton")
        self.lineEdit = QtWidgets.QLineEdit(Form)
        self.lineEdit.setGeometry(QtCore.QRect(230, 100, 481, 201))
        self.lineEdit.setObjectName("lineEdit")

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.pushButton.setText(_translate("Form", "PushButton"))

class Main(QtWidgets.QWidget, Ui_Form): 
    def __init__(self, parent=None):
        super(Main, self).__init__(parent) 
        
        self.setupUi(self)

        self.w = self.size().width()     # "определение ширины"
        self.h = self.size().height()    # "определение высоты"
        
    def resizeEvent(self, event):        
        width =  self.size().width()    
        height = self.size().height()   
        
        koefW = width / self.w 
        koefH = height / self.h 
        
        self.pushButton.setGeometry(200 * koefW, 510 * koefH, 541 * koefW, 121 * koefH)
        self.lineEdit.setGeometry(230 * koefW, 100 * koefH, 481 * koefW, 201 * koefH)


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