Python + PyQt5 to achieve homemade pdf toolkit

import sys
import os
from  import QApplication, QMainWindow, QPushButton, QVBoxLayout, QWidget, QFileDialog, QListWidget, QMessageBox, QLineEdit, QHBoxLayout, QInputDialog
from  import Qt, QThread, pyqtSignal
from PyPDF2 import PdfReader, PdfWriter, PdfMerger
from PyQt5 import QtGui

class CustomListWidget(QListWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

class Worker(QThread):
    finished = pyqtSignal(str)
    error = pyqtSignal(str)
    def __init__(self, pdf_files, range_str=None, save_path=None, operation=None):
        super().__init__()
        self.pdf_files = pdf_files
        self.range_str = range_str
        self.save_path = save_path
         = operation
    def run(self):
        try:
            if  == 'merge':
                merger = PdfMerger()
                for pdf in self.pdf_files:
                    (pdf)
                (self.save_path)
                ()
                ('The PDF files have been successfully merged.')
            elif  == 'split':
                start_page, end_page = self.parse_range(self.range_str)
                reader = PdfReader(self.pdf_files[zxsq-anti-bbcode-0])
                (self.save_path, exist_ok=True)
                for page in range(start_page, end_page + 1):
                    writer = PdfWriter()
                    writer.add_page()
                    split_save_path = (self.save_path, f'Page_{page + 1}.pdf')
                    (split_save_path)
                ('The PDF file has been successfully split and saved.')
            elif  == 'delete':
                start_page, end_page = self.parse_range(self.range_str)
                reader = PdfReader(self.pdf_files[zxsq-anti-bbcode-0])
                writer = PdfWriter()
                for page_num in range(len()):
                    if not (start_page <= page_num <= end_page):
                        writer.add_page([zxsq-anti-bbcode-page_num])
                (self.save_path)
                ('The specified page has been removed from the PDF.')
        except Exception as e:
            (str(e))
    def parse_range(self, range_str):
        if '-' in range_str:
            start_page, end_page = map(int, range_str.split('-'))
        else:
            start_page = end_page = int(range_str)
        return start_page - 1, end_page - 1  # Convert to 0-based index

class PDFMergerApp(QMainWindow):
    def __init__(self):
        super().__init__()
        ()
        self.pdf_files = []
    def initUI(self):
        ('PDF Toolbox')
        ((''))
        (100, 100, 800, 600)
        mainLayout = QVBoxLayout()
         = QPushButton('Add PDF', self)
        ()
        ()
         = CustomListWidget(self)
        ()
        # Delete button horizontal layout
        deleteLayout = QHBoxLayout()
         = QPushButton('Delete selected', self)
        ()
        ()
         = QPushButton('Delete All', self)
        ()
        ()
        (deleteLayout)
         = QPushButton('Merge PDFs', self)
        ()
        ()
        # Horizontal layout for splitting and deleting page numbers
        splitDeleteLayout = QHBoxLayout()
         = QLineEdit(self)
        ('Enter the split range, e.g. 1 or 1-4')
        ()
         = QPushButton('Split PDF', self)
        ()
        ()
         = QLineEdit(self)
        ('Enter the deleted page number, e.g. 1 or 1-4')
        ()
         = QPushButton('Delete page', self)
        ()
        ()
        (splitDeleteLayout)
        container = QWidget()
        (mainLayout)
        (container)
    def addPDF(self):
        files, _ = (self, 'Open file', '', 'PDF files (*.pdf)')
        for file_path in files:
            (file_path)
    def addPDFFile(self, file_path):
        if file_path and file_path not in self.pdf_files:
            self.pdf_files.append(file_path)
            (file_path)
    def removeSelected(self):
        for item in ():
            self.pdf_files.remove(())
            ((item))
    def removeAll(self):
        self.pdf_files.clear()
        ()
    def mergePDFs(self):
        save_path, _ = (self, 'Save file', '', 'PDF files (*.pdf)')
        if save_path:
             = Worker(self.pdf_files, save_path=save_path, operation='merge')
            ()
            ()
            ()
    def splitPDF(self):
        if len(self.pdf_files) != 1:
            (self, "Error.", "Please select only one PDF file to split.")
            return
        range_str = ().strip()
        folder_path = ()
        if range_str and folder_path:
             = Worker(self.pdf_files, range_str=range_str, save_path=folder_path, operation='split')
            ()
            ()
            ()
    def getFolderName(self):
        folder_path = (self, "Choose where to save the split file")
        if folder_path:
            folder_name, ok = (self, "Folder name", "Enter folder name:")
            if ok and folder_name:
                full_path = (folder_path, folder_name)
                (full_path, exist_ok=True)
                return full_path
        return None
    def deletePages(self):
        if len(self.pdf_files) != 1:
            (self, "Error.", "Please select only one PDF file for deletion operation.")
            return
        range_str = ().strip()
        save_path = (self, 'Save file', '', 'PDF files (*.pdf)')[zxsq-anti-bbcode-0]
        if save_path and range_str:
             = Worker(self.pdf_files, range_str=range_str, save_path=save_path, operation='delete')
            ()
            ()
            ()
    def onFinished(self, message):
        self.show_message("Operation complete.", message)
        self.clear_pdf_list()
    def onError(self, error_message):
        self.show_message("Operation failed.", error_message)
    def show_message(self, title, message):
        (self, title, message)
    def clear_pdf_list(self):
        self.pdf_files.clear()
        ()
def main():
    app = QApplication()
    ex = PDFMergerApp()
    ()
    (app.exec_())

if __name__ == '__main__':
    main()