pyqt5 qthread crash for unkown reason,how to use it correctly？

Question

I am new to pyqt5 and I find a wield problem that I can't explain

First of all,I figure I should use QObject rather than Qthread directly when I try to solve this problem in my own way,but I just curious why this happened

If I use Qthread(self)，and the program works fine, but if I use Qthread(),don't pass self to Qthread parent, the program crashes. This is not weild, what is weild is that I use Qthread(), and add a line time.sleep(0.1),the code works fine too, I couldn't figure out why, can someone explain it.

I use Python a lot, but new to pyqt5, and it code is in C++， I can't read the source code to find why. here is my code:

from PyQt5.QtWidgets import QWidget, QPushButton, QApplication, QGridLayout
from PyQt5.QtCore import QThread
import sys
import time
import threading


class MyThread(QThread):
    def run(self):
        print('working', threading.current_thread())


class MyHelper(QWidget):

    def __init__(self):
        super(MyHelper, self).__init__()
        self.init_ui()

    def init_ui(self):
        self.submit_button = QPushButton('submit')
        self.submit_button.clicked.connect(self.click_op)
        self.my_grid = QGridLayout()
        self.my_grid.addWidget(self.submit_button, 1, 1)
        self.setLayout(self.my_grid)
        self.setGeometry(300, 300, 350, 300)
        self.show()

    def click_op(self):
        '''
            my_sender = MyThread()  crash
            my_sender = MyThread(self) OK
            my_sender = MyThread() + time.sleep(0.1) OK, most weild one
        '''
        my_sender = MyThread()
        # my_sender = MyThread(self)
        my_sender.start()
        time.sleep(0.1)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    email_helper = MyHelper()
    exit(app.exec_())

Answer 1

Local variables are automatically destroyed at the end of the function, declaring my_sender as a class variable

self.my_sender = MyThread()
self.my_sender.start()