Присвоение текста одного поля другому PyQt

Не изменяйте код, сгенерированный Qt Designer. Создайте другой класс, который наследуется от соответствующего виджета, и используйте созданный класс для его заполнения.

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(2417, 957)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setGeometry(QtCore.QRect(0, 0, 2421, 921))
        self.tabWidget.setMinimumSize(QtCore.QSize(801, 0))
        self.tabWidget.setObjectName("tabWidget")
        self.tab = QtWidgets.QWidget()
        self.tab.setObjectName("tab")
        self.pushButton = QtWidgets.QPushButton(self.tab)
        self.pushButton.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton.setObjectName("pushButton")
        self.textEdit_2 = QtWidgets.QTextEdit(self.tab)
        self.textEdit_2.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_2.setObjectName("textEdit_2")
        self.label = QtWidgets.QLabel(self.tab)
        self.label.setGeometry(QtCore.QRect(36, 20, 101, 20))
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.tab)
        self.label_2.setGeometry(QtCore.QRect(260, 20, 441, 20))
        self.label_2.setObjectName("label_2")
        self.lineEdit = QtWidgets.QLineEdit(self.tab)
        self.lineEdit.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit.setObjectName("lineEdit")
        self.tabWidget.addTab(self.tab, "")
        self.tab_3 = QtWidgets.QWidget()
        self.tab_3.setObjectName("tab_3")
        self.textEdit_5 = QtWidgets.QTextEdit(self.tab_3)
        self.textEdit_5.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_5.setObjectName("textEdit_5")
        self.pushButton_3 = QtWidgets.QPushButton(self.tab_3)
        self.pushButton_3.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton_3.setObjectName("pushButton_3")
        self.label_5 = QtWidgets.QLabel(self.tab_3)
        self.label_5.setGeometry(QtCore.QRect(36, 22, 111, 16))
        self.label_5.setObjectName("label_5")
        self.label_6 = QtWidgets.QLabel(self.tab_3)
        self.label_6.setGeometry(QtCore.QRect(260, 15, 431, 31))
        self.label_6.setObjectName("label_6")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.tab_3)
        self.lineEdit_2.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.tabWidget.addTab(self.tab_3, "")
        self.tab_2 = QtWidgets.QWidget()
        self.tab_2.setObjectName("tab_2")
        self.label_3 = QtWidgets.QLabel(self.tab_2)
        self.label_3.setGeometry(QtCore.QRect(36, 20, 101, 20))
        self.label_3.setObjectName("label_3")
        self.textEdit_4 = QtWidgets.QTextEdit(self.tab_2)
        self.textEdit_4.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_4.setObjectName("textEdit_4")
        self.label_4 = QtWidgets.QLabel(self.tab_2)
        self.label_4.setGeometry(QtCore.QRect(260, 20, 441, 20))
        self.label_4.setObjectName("label_4")
        self.pushButton_2 = QtWidgets.QPushButton(self.tab_2)
        self.pushButton_2.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton_2.setObjectName("pushButton_2")
        self.lineEdit_3 = QtWidgets.QLineEdit(self.tab_2)
        self.lineEdit_3.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit_3.setObjectName("lineEdit_3")
        self.tabWidget.addTab(self.tab_2, "")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 2417, 20))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Punch!"))
        self.label.setText(_translate("MainWindow", "               IP"))
        self.label_2.setText(_translate("MainWindow", "                                                              Work place"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab), _translate("MainWindow", "Whois Function"))
        self.pushButton_3.setText(_translate("MainWindow", "Punch!"))
        self.label_5.setText(_translate("MainWindow", "               IP"))
        self.label_6.setText(_translate("MainWindow", "                                                              Work place"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_3), _translate("MainWindow", "Port Scanner "))
        self.label_3.setText(_translate("MainWindow", "               IP"))
        self.label_4.setText(_translate("MainWindow", "                                                              Work place"))
        self.pushButton_2.setText(_translate("MainWindow", "Punch!"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_2), _translate("MainWindow", "Blacklists checkout "))


class Window(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super(Window, self).__init__()
        self.setupUi(self)

        self.pushButton.clicked.connect(self.on_button_click)

    def on_button_click(self):
        self.textEdit_2.setText(self.lineEdit.text())


if __name__ == '__main__':
    import sys
    
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle('Fusion')
    w = Window()
    w.show()
    sys.exit(app.exec_())

У вас там будет ошибка:

AttributeError: 'bool' object has no attribute 'textEdit_2'

Причина в том, что сигнал clicked у кнопки передает флаг checked у самой кнопки, поэтому в функцию on_button_click и передается значение bool

А вам нужно работать с самими виджетами.

Первый вариант. Работать напрямую через ui:

...
    def on_button_click():
        ui.textEdit_2.setText(ui.lineEdit.text())

    ui.pushButton.clicked.connect(on_button_click)
...

Второй вариант. Сделайте свой виджет и в нем используйте ту функцию. Думаю, это самый правильный.

Весь код:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(2417, 957)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setGeometry(QtCore.QRect(0, 0, 2421, 921))
        self.tabWidget.setMinimumSize(QtCore.QSize(801, 0))
        self.tabWidget.setObjectName("tabWidget")
        self.tab = QtWidgets.QWidget()
        self.tab.setObjectName("tab")
        self.pushButton = QtWidgets.QPushButton(self.tab)
        self.pushButton.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton.setObjectName("pushButton")
        self.textEdit_2 = QtWidgets.QTextEdit(self.tab)
        self.textEdit_2.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_2.setObjectName("textEdit_2")
        self.label = QtWidgets.QLabel(self.tab)
        self.label.setGeometry(QtCore.QRect(36, 20, 101, 20))
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.tab)
        self.label_2.setGeometry(QtCore.QRect(260, 20, 441, 20))
        self.label_2.setObjectName("label_2")
        self.lineEdit = QtWidgets.QLineEdit(self.tab)
        self.lineEdit.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit.setObjectName("lineEdit")
        self.tabWidget.addTab(self.tab, "")
        self.tab_3 = QtWidgets.QWidget()
        self.tab_3.setObjectName("tab_3")
        self.textEdit_5 = QtWidgets.QTextEdit(self.tab_3)
        self.textEdit_5.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_5.setObjectName("textEdit_5")
        self.pushButton_3 = QtWidgets.QPushButton(self.tab_3)
        self.pushButton_3.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton_3.setObjectName("pushButton_3")
        self.label_5 = QtWidgets.QLabel(self.tab_3)
        self.label_5.setGeometry(QtCore.QRect(36, 22, 111, 16))
        self.label_5.setObjectName("label_5")
        self.label_6 = QtWidgets.QLabel(self.tab_3)
        self.label_6.setGeometry(QtCore.QRect(260, 15, 431, 31))
        self.label_6.setObjectName("label_6")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.tab_3)
        self.lineEdit_2.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.tabWidget.addTab(self.tab_3, "")
        self.tab_2 = QtWidgets.QWidget()
        self.tab_2.setObjectName("tab_2")
        self.label_3 = QtWidgets.QLabel(self.tab_2)
        self.label_3.setGeometry(QtCore.QRect(36, 20, 101, 20))
        self.label_3.setObjectName("label_3")
        self.textEdit_4 = QtWidgets.QTextEdit(self.tab_2)
        self.textEdit_4.setGeometry(QtCore.QRect(260, 40, 441, 291))
        self.textEdit_4.setObjectName("textEdit_4")
        self.label_4 = QtWidgets.QLabel(self.tab_2)
        self.label_4.setGeometry(QtCore.QRect(260, 20, 441, 20))
        self.label_4.setObjectName("label_4")
        self.pushButton_2 = QtWidgets.QPushButton(self.tab_2)
        self.pushButton_2.setGeometry(QtCore.QRect(30, 302, 111, 31))
        self.pushButton_2.setObjectName("pushButton_2")
        self.lineEdit_3 = QtWidgets.QLineEdit(self.tab_2)
        self.lineEdit_3.setGeometry(QtCore.QRect(40, 40, 91, 20))
        self.lineEdit_3.setObjectName("lineEdit_3")
        self.tabWidget.addTab(self.tab_2, "")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 2417, 20))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Punch!"))
        self.label.setText(_translate("MainWindow", "               IP"))
        self.label_2.setText(
            _translate("MainWindow", "                                                              Work place"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab), _translate("MainWindow", "Whois Function"))
        self.pushButton_3.setText(_translate("MainWindow", "Punch!"))
        self.label_5.setText(_translate("MainWindow", "               IP"))
        self.label_6.setText(
            _translate("MainWindow", "                                                              Work place"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_3), _translate("MainWindow", "Port Scanner "))
        self.label_3.setText(_translate("MainWindow", "               IP"))
        self.label_4.setText(
            _translate("MainWindow", "                                                              Work place"))
        self.pushButton_2.setText(_translate("MainWindow", "Punch!"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_2), _translate("MainWindow", "Blacklists checkout "))


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.ui.pushButton.clicked.connect(self.on_button_click)

    def on_button_click(self):
        self.ui.textEdit_2.setText(self.ui.lineEdit.text())


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)

    mw = MainWindow()
    mw.show()

    sys.exit(app.exec_())