為什么會(huì)顯示{'s': 'My First App', 'a': 100}

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *

import sys

class MainWindow(QMainWindow):

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    self.windowTitleChanged.connect(self._my_func)
    self.setWindowTitle('My First App')

    label = QLabel('Welcome to Shiyanlou!')
    label.setAlignment(Qt.AlignCenter)
    self.setCentralWidget(label)

def _my_func(self, s='my_func', a=100):
    dic = {'s': s, 'a': a}
    print(dic)

app = QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec_()

'My First App'哪里來(lái)的