AttributeError: 'NoneType' object has no attribute 'update' when trying to add files to a csv file

Question

I've been working on an expense manager in python where you can import you spending from CSV file add more put them in a chart etc then you could export the info into CSV file but then faced this problem

AttributeError: 'NoneType' object has no attribute 'update'

I tried rewriting a bunch of code to no avail

here's the code

Add dependencies

import csv

import sys
from PySide6.QtCore import Qt, Slot
from PySide6.QtGui import QAction , QPainter
from PySide6.QtWidgets import (QApplication, QHeaderView, QHBoxLayout, QLabel, QLineEdit, 
                               QMainWindow, QPushButton, QTableWidget, QTableWidgetItem, QVBoxLayout, 
                               QWidget)
from PySide6.QtCharts import QChartView, QPieSeries, QChart





class Widget(QWidget):
    def __init__(self):
        QWidget.__init__(self)
        self.items = 0
        self._data = {}
        
        with open('aib_october.csv', encoding= 'utf-8-sig') as f:
            reader = csv.DictReader(f)
            for record in reader:
                self._data.update(record)

        print(self._data) 

        # Left Widget
        self.table = QTableWidget()
        self.table.setColumnCount(2)
        self.table.setHorizontalHeaderLabels(["Description", "Price"])
        self.table.horizontalHeader().setSectionResizeMode(QHeaderView.Stretch)

        # Chart
        self.chart_view = QChartView()
        self.chart_view.setRenderHint(QPainter.Antialiasing)

        # Right Widget
        self.description = QLineEdit()
        self.price = QLineEdit()
        self.add = QPushButton("Add")
        self.clear = QPushButton("Clear")
        self.quit = QPushButton("Quit")
        self.plot = QPushButton("Plot")
        self.export = QPushButton("export")

        # Disabling 'Add' button
        self.add.setEnabled(False)

        self.right = QVBoxLayout()
        self.right.addWidget(QLabel("Description"))
        self.right.addWidget(self.description)
        self.right.addWidget(QLabel("Price"))
        self.right.addWidget(self.price)
        self.right.addWidget(self.add)
        self.right.addWidget(self.plot)
        self.right.addWidget(self.chart_view)
        self.right.addWidget(self.export)
        self.right.addWidget(self.clear)
        self.right.addWidget(self.quit)

        # QWidget Layout
        self.layout = QHBoxLayout()

        #self.table_view.setSizePolicy(size)
        self.layout.addWidget(self.table)
        self.layout.addLayout(self.right)

        # Set the layout to the QWidget
        self.setLayout(self.layout)

        # Signals and Slots
        self.add.clicked.connect(self.add_element)
        self.quit.clicked.connect(self.quit_application)
        self.plot.clicked.connect(self.plot_data)
        self.clear.clicked.connect(self.clear_table)
        self.export.clicked.connect(self.export_data)
        self.description.textChanged[str].connect(self.check_disable)
        self.price.textChanged[str].connect(self.check_disable)

        # Fill example data
        self.fill_table()

    @Slot()

    def export_data(self):
        with open("aib_october.csv", 'w', newline='') as file:
                writer = csv.DictWriter(file,fieldnames=self._data.keys())
                writer.writeheader()
                writer.writerow(self._data)

    def add_element(self):
        des = self.description.text()
        price = self.price.text()

        try:
            price_item = QTableWidgetItem(f"{float(price):.2f}")
            price_item.setTextAlignment(Qt.AlignRight)

            self.table.insertRow(self.items)
            description_item = QTableWidgetItem(des)

            self.table.setItem(self.items, 0, description_item)
            self.table.setItem(self.items, 1, price_item)

            self.description.setText("")
            self.price.setText("")

            self.items += 1
            self._data.update(self.description.text())
            self._data.update(self.price.text())
            print(self._data)
        except ValueError:
            print("That is not an invalid input:", price, "Make sure to enter a price!")


    @Slot()
    def check_disable(self, x):
        if not self.description.text() or not self.price.text():
            self.add.setEnabled(False)
        else:
            self.add.setEnabled(True)

    @Slot()
    def plot_data(self):
        # Get table information
        series = QPieSeries()
        for i in range(self.table.rowCount()):
            text = self.table.item(i, 0).text()
            number = float(self.table.item(i, 1).int())
            series.append(text, number)

        chart = QChart()
        chart.addSeries(series)
        chart.legend().setAlignment(Qt.AlignLeft)
        self.chart_view.setChart(chart)

    @Slot()
    def quit_application(self):
        QApplication.quit()

    def fill_table(self, data=None):
        data = self._data if not data else data
        for desc, price in data.items():
            description_item = QTableWidgetItem(desc)
            price_item = QTableWidgetItem("{}".format(price))
            price_item.setTextAlignment(Qt.AlignRight)
            self.table.insertRow(self.items)
            self.table.setItem(self.items, 0, description_item)
            self.table.setItem(self.items, 1, price_item)
            self.items += 1
            self._data = self._data.update({desc: price})
            print(self._data)

    @Slot()
    def clear_table(self):
        self.table.setRowCount(0)
        self.items = 0
        self._data = {}


class MainWindow(QMainWindow):
    def __init__(self, widget):
        QMainWindow.__init__(self)
        self.setWindowTitle("The pynancial advisor")

        # Menu
        self.menu = self.menuBar()
        self.file_menu = self.menu.addMenu("File")

        # Exit QAction
        exit_action = QAction("Exit", self)
        exit_action.setShortcut("Ctrl+Q")
        exit_action.triggered.connect(self.exit_app)

        self.file_menu.addAction(exit_action)
        self.setCentralWidget(widget)

    @Slot()
    def exit_app(self, checked):
        QApplication.quit()


if __name__ == "__main__":
    # Qt Application
    app = QApplication(sys.argv)
    # QWidget
    widget = Widget()
    # QMainWindow using QWidget as central widget
    window = MainWindow(widget)
    window.resize(800, 600)
    window.show()

    # Execute application
    sys.exit(app.exec())