Cuando intento obtener el texto del qtextedit creado con PyQt5 Designer, aparece un error o "Python deja de funcionar" y el script se detiene automáticamente. He intentado múltiples soluciones pero nada funciona. Tengo que asignar el texto de qtextedit a una variable, para verificar si el proceso se ejecuta o no. Ese es el código generado por PyQt5:

from PyQt5 import QtCore, QtGui, QtWidgets
import psutil
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(221, 157)
        MainWindow.setMinimumSize(QtCore.QSize(221, 157))
        MainWindow.setMaximumSize(QtCore.QSize(221, 157))
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.cercaprocesso = QtWidgets.QPushButton(self.centralwidget)
        self.cercaprocesso.setGeometry(QtCore.QRect(0, 80, 221, 31))
        font = QtGui.QFont()
        font.setFamily("MS Shell Dlg 2")
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.cercaprocesso.setFont(font)
        self.cercaprocesso.setObjectName("pushButton")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(0, 0, 221, 40))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label.setFont(font)
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")
        self.textbox = QtWidgets.QTextEdit(self.centralwidget)
        self.textbox.setGeometry(QtCore.QRect(30, 40, 161, 31))
        self.textbox.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.textbox.setObjectName("textEdit")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 221, 21))
        self.menubar.setObjectName("menubar")
        self.menucredit = QtWidgets.QMenu(self.menubar)
        self.menucredit.setObjectName("menucredit")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.actionbot_created_by_andrea1980345_inforge_user = QtWidgets.QAction(MainWindow)     
        self.actionbot_created_by_andrea1980345_inforge_user.setObjectName ("actionbot")
        self.menucredit.addAction(self.actionbot_created_by_andrea1980345_inforge_user)
        self.menubar.addAction(self.menucredit.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

Código del botón aquí:

def retranslateUi(self, MainWindow):
    _translate = QtCore.QCoreApplication.translate
    MainWindow.setWindowTitle(_translate("MainWindow", "andrea1980345 Bot"))
    self.cercaprocesso.setText(_translate("MainWindow", "Cerca Processo"))
    self.label.setText(_translate("MainWindow", "Inserire il nome del processo"))
    self.menucredit.setTitle(_translate("MainWindow", "Credit"))
    self.actionbot_created_by_andrea1980345_inforge_user.setText(_translate("MainWindow", "bot"))
    self.cercaprocesso.clicked.connect(self.search)

Aquí el código para obtener el texto del cuadro de texto y asignarlo a una variable:

def search(self):
    textboxValue = self.textbox.text()
    for pid in psutil.pids():  # Controlla se il processo è attivo
        listapid = psutil.Process(pid)
        if listapid.name() == textboxValue:
            print('Processo trovato')
    self.textbox.setText("")

Código final:

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())