如何通过单击其中的按钮来获取列表小部件中元素的索引。Pyside6

我为你标记了你犯的两个错误。问有什么不清楚的。

import sys
'''
from PySide6 import QtWidgets
from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
    QMetaObject, QObject, QPoint, QRect,
    QSize, QTime, QUrl, Qt)
from PySide6.QtGui import (QBrush, QColor, QConicalGradient, QCursor,
    QFont, QFontDatabase, QGradient, QIcon,
    QImage, QKeySequence, QLinearGradient, QPainter,
    QPalette, QPixmap, QRadialGradient)
from PySide6.QtWidgets import *
'''
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


class Ui_Form(object):
    def setupUi(self, Form):
        if not Form.objectName():
            Form.setObjectName(u"Form")
        Form.resize(291, 53)
        self.horizontalLayout = QHBoxLayout(Form)
        self.horizontalLayout.setObjectName(u"horizontalLayout")
        self.label = QLabel(Form)
        self.label.setObjectName(u"label")
        self.label.setMinimumSize(QSize(200, 20))

        self.horizontalLayout.addWidget(self.label)

        self.pushButton = QPushButton(Form)
        self.pushButton.setObjectName(u"pushButton")
        self.pushButton.setMinimumSize(QSize(50, 20))

        self.horizontalLayout.addWidget(self.pushButton)

        self.retranslateUi(Form)

        QMetaObject.connectSlotsByName(Form)
    # setupUi

    def retranslateUi(self, Form):
        Form.setWindowTitle(QCoreApplication.translate("Form", u"Form", None))
        self.label.setText(QCoreApplication.translate("Form", u"\u0422\u0443\u0442 \u0434\u043e\u043b\u0436\u0435\u043d \u0431\u044b\u0442\u044c \u0442\u0435\u043a\u0441\u0442", None))
        self.pushButton.setText(QCoreApplication.translate("Form", u"PushButton", None))
    # retranslateUi


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        if not MainWindow.objectName():
            MainWindow.setObjectName(u"MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QWidget(MainWindow)
        self.centralwidget.setObjectName(u"centralwidget")
        self.gridLayout = QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName(u"gridLayout")
        self.listWidget = QListWidget(self.centralwidget)
        self.listWidget.setObjectName(u"listWidget")

        self.gridLayout.addWidget(self.listWidget, 0, 0, 1, 1)

        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QMenuBar(MainWindow)
        self.menubar.setObjectName(u"menubar")
        self.menubar.setGeometry(QRect(0, 0, 800, 22))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QStatusBar(MainWindow)
        self.statusbar.setObjectName(u"statusbar")
        MainWindow.setStatusBar(self.statusbar)

        QMetaObject.connectSlotsByName(MainWindow)


#class TestWidget(QtWidgets.QMainWindow, Ui_Form):
#                          vvvvvvv
class TestWidget(QtWidgets.QWidget, Ui_Form):                                           # +++
    def __init__(self, parent=None):
        super(TestWidget, self).__init__(parent)
        self.setupUi(self)
    # setupUi

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
    # retranslateUi

    def setText(self, text):
        self.label.setText(text)

    def sizeHint(self):
        return QSize(200, 40)


class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.setupUi(self)
        
        for i in range(20):
            testwidget = TestWidget()
            item = QtWidgets.QListWidgetItem(self.listWidget)
            testwidget.setText(f"Это элемент {i}")
# +++                        
#            testwidget.pushButton.clicked.connect(lambda: self.test(i))                                      
            testwidget.pushButton.clicked.connect(lambda ch, i=i: self.test(i))          # +++
            
            item.setSizeHint(testwidget.sizeHint())
            self.listWidget.addItem(item)
            self.listWidget.setItemWidget(item, testwidget)

    def test(self, i):
        print("Элемент", i)


if __name__ == "__main__":
    if not QtWidgets.QApplication.instance():
        app = QtWidgets.QApplication(sys.argv)
    else:
        app = QtWidgets.QApplication.instance()
    window = MainWindow()
    window.show()
    sys.exit(app.exec())