pyqt5: why the mimeData().text() returns nothing?

Question

learning PyQt5 recently, I've tried to drag a QPushButton learning this tutorial Drag & drop a button widget, and made some improvements to place the button more accurate, so I add mime = e.mimeData().text() x, y = mime.split(',') according to @Avaris for this question, but I found e.mimeData().text() returned nothing which supposed to be the coordinate of local position of the cursor with respect to the button, i tried to print(mime), and got a blank line with nothing, then i print(mime.split(',')) and got ['']。

here's the code:

import sys
from PyQt5.QtWidgets import QPushButton, QWidget, QApplication, QLabel
from PyQt5.QtCore import Qt, QMimeData
from PyQt5.QtGui import QDrag
from PyQt5 import QtCore


class Button(QPushButton):

    def __init__(self, title, parent):
        super().__init__(title, parent)

    def mouseMoveEvent(self, e):

        if e.buttons() != Qt.RightButton:
            return

        mimeData = QMimeData()

        drag = QDrag(self)
        drag.setMimeData(mimeData)

       dropAction = drag.exec_(Qt.MoveAction)

    def mousePressEvent(self, e):

        QPushButton.mousePressEvent(self, e)

        if e.button() == Qt.LeftButton:
            print('press')


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):

        self.setAcceptDrops(True)

        self.button = Button('Button', self)
        self.button.move(100, 65)

        self.setWindowTitle('Click or Move')
        self.setGeometry(300, 300, 280, 150)

    def dragEnterEvent(self, e):

        e.accept()

    def dropEvent(self, e):

        position = e.pos()
        mime = e.mimeData().text()
        x, y = mime.split(',')

        #print(mime.split(','))

        self.button.move(position - QtCore.QPoint(int(x), int(y)))

        e.setDropAction(Qt.MoveAction)
        e.accept()


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()

Answer 1

In the answer of @Avaris, you will notice they set the mimedata with the button position in the mouseMoveEvent:

mimeData = QtCore.QMimeData()
# simple string with 'x,y'
mimeData.setText('%d,%d' % (e.x(), e.y()))

The mimedata does not contain anything by default. You have to set everything yourself! Have a look at the documentation for QMimeData to see what else you can do (other than setting arbitrary text)