Step1: Enable Accept Drops APP Main Window

self.setAcceptDrops(True)

Step2 Implement Drag Event Handler

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            event.ignore()

Step3 Implement Drop Event Handler

    def dropEvent(self, event):
        files = [u.toLocalFile() for u in event.mimeData().urls()]
        for f in files:
            print(f)

Whole code

from PyQt5.QtWidgets import QMainWindow, QApplication
import sys


class MainWidget(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Drag and Drop")
        self.resize(720, 480)
        '''Step1: Enable Accept Drops APP Main Window'''
        self.setAcceptDrops(True)

    '''Step2 Implement Drag Event Handler'''
    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            event.ignore()

    '''Step3 Implement Drop Event Handler'''
    def dropEvent(self, event):
        files = [u.toLocalFile() for u in event.mimeData().urls()]
        for f in files:
            print(f)


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