import sys

from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QLabel, QLineEdit
from PyQt5.QtWidgets import QGridLayout


class MyWidget(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setWindowTitle("Aufgabe 43")

        grid = QGridLayout()
        grid.addWidget(QLabel("Dezimalzahl", self), 0, 0)
        grid.addWidget(QLabel("Hexzahl", self), 1, 0)

        self.d=QLineEdit()
        grid.addWidget(self.d, 0, 1, 1, 2)

        self.h=QLineEdit()
        grid.addWidget(self.h, 1, 1, 1, 2)

        self.b=QPushButton("Berechnung", self)
        grid.addWidget(self.b, 2, 0, 1, 3)
        self.b.clicked.connect(self.calc)

        self.setLayout(grid)
        self.show()



    def calc(self):
        text = self.d.text()

        try:
            zahl = hex(int(text))
            self.h.setText(zahl)
        except:
            self.h.setText("")




app = QApplication(sys.argv)
w=MyWidget()
sys.exit(app.exec_())