In the example below, which produces this GUI:

… if I click the close button on tab 2 (or tab 3), then on_tab_close handler fires/is triggered/runs.

However, if I click the button “Close tab 2” which calls .removeTab, then tab 2 is indeed removed, but the on_tab_close handler does not fire.

How can I programmatically close tab 2 (here, by clicking the button “Close tab 2”), in a way that will also trigger the on_tab_close handler?

#!/usr/bin/env python3

import sys
from PyQt5.QtWidgets import (QMainWindow, QApplication, QPushButton, QWidget, QAction, QTabWidget, QVBoxLayout, QLabel, QVBoxLayout, QStyle)

class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QTabWidget test")
        self.setGeometry(0, 0, 300, 200)

        self.cent_widget = QWidget(self)
        self.setCentralWidget(self.cent_widget)
        self.vlayout = QVBoxLayout(self.cent_widget)

        self.close_btn = QPushButton("Close tab 2")
        self.close_btn.clicked.connect(self.on_close_btn)
        self.vlayout.addWidget(self.close_btn)

        self.tabswidget = QTabWidget()
        self.vlayout.addWidget(self.tabswidget)

        self.tab1 = QLabel("This is tab 1.")
        self.tab2 = QLabel("This is tab 2.")
        self.tab3 = QLabel("This is tab 3.")

        self.tabswidget.addTab(self.tab1, "Tab 1")
        self.tabswidget.addTab(self.tab2, "Tab 2")
        self.tabswidget.addTab(self.tab3, "Tab 3")

        self.tabswidget.setTabsClosable(True) # /q/60409663
        default_side = self.tabswidget.style().styleHint(
            QStyle.SH_TabBar_CloseButtonPosition, None, self.tabswidget.tabBar()
        )
        self.tabswidget.tabBar().setTabButton(0, default_side, None)

        self.tabswidget.tabCloseRequested.connect(self.tabswidget.removeTab) # /q/19151159
        self.tabswidget.tabCloseRequested.connect(self.on_tab_close)

        self.show()

    def on_close_btn(self):
        print("on_close_btn")
        self.tabswidget.removeTab( self.tabswidget.indexOf(self.tab2)  )

    def on_tab_close(self):
        print("on_tab_close")


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = MyWindow()
    sys.exit(app.exec_())