import sys
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QMainWindow
from PyQt5.QtWidgets import QPushButton
from PyQt5.QtWidgets import QMessageBox


class MainWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        pybutton = QPushButton('йух', self)
        pybutton.clicked.connect(self.clickMethod)

    def clickMethod(self):
        QMessageBox.about(self, "Title", "Хуй")


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())