Welcome folks today in this post we will be creating a advanced notepad which supports crud operations and also various other advanced features in pyqt5 library which is useful creating gui applications in python. All the full source code of the application will be given below.

Get Started

In order to get started you need to install the following library by pip command as shown below

pip install pyqt5

After installing this library make an app.py file and copy paste the following code to it

app.py

# importing required libraries 
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtPrintSupport import *
import os 
import sys 

# Creating main window class 
class MainWindow(QMainWindow): 

    # constructor 
    def __init__(self, *args, **kwargs): 
        super(MainWindow, self).__init__(*args, **kwargs) 

        # setting window geometry 
        self.setGeometry(100, 100, 600, 400) 

        # creating a layout 
        layout = QVBoxLayout() 

        # creating a QPlainTextEdit object 
        self.editor = QPlainTextEdit() 

        # setting font to the editor 
        fixedfont = QFontDatabase.systemFont(QFontDatabase.FixedFont) 
        fixedfont.setPointSize(12) 
        self.editor.setFont(fixedfont) 

        # self.path holds the path of the currently open file. 
        # If none, we haven't got a file open yet (or creating new). 
        self.path = None

        # adding editor to the layout 
        layout.addWidget(self.editor) 

        # creating a QWidget layout 
        container = QWidget() 

        # setting layout to the container 
        container.setLayout(layout) 

        # making container as central widget 
        self.setCentralWidget(container) 

        # creating a status bar object 
        self.status = QStatusBar() 

        # setting stats bar to the winow 
        self.setStatusBar(self.status) 

        # creating a file tool bar 
        file_toolbar = QToolBar("File") 

        # adding file tool bar to the window 
        self.addToolBar(file_toolbar) 

        # creating a file menu 
        file_menu = self.menuBar().addMenu("&File") 

        # creating actions to add in the file menu 
        # creating a open file action 
        open_file_action = QAction("Open file", self) 

        # setting status tip 
        open_file_action.setStatusTip("Open file") 

        # adding action to the open file 
        open_file_action.triggered.connect(self.file_open) 

        # adding this to file menu 
        file_menu.addAction(open_file_action) 

        # adding this to tool bar 
        file_toolbar.addAction(open_file_action) 

        # similarly creating a save action 
        save_file_action = QAction("Save", self) 
        save_file_action.setStatusTip("Save current page") 
        save_file_action.triggered.connect(self.file_save) 
        file_menu.addAction(save_file_action) 
        file_toolbar.addAction(save_file_action) 

        # similarly creating save action 
        saveas_file_action = QAction("Save As", self) 
        saveas_file_action.setStatusTip("Save current page to specified file") 
        saveas_file_action.triggered.connect(self.file_saveas) 
        file_menu.addAction(saveas_file_action) 
        file_toolbar.addAction(saveas_file_action) 

        # for print action 
        print_action = QAction("Print", self) 
        print_action.setStatusTip("Print current page") 
        print_action.triggered.connect(self.file_print) 
        file_menu.addAction(print_action) 
        file_toolbar.addAction(print_action) 

        # creating another tool bar for editing text 
        edit_toolbar = QToolBar("Edit") 

        # adding this tool bar to the main window 
        self.addToolBar(edit_toolbar) 

        # creating a edit menu bar 
        edit_menu = self.menuBar().addMenu("&Edit") 

        # adding actions to the tool bar and menu bar 

        # undo action 
        undo_action = QAction("Undo", self) 
        # adding status tip 
        undo_action.setStatusTip("Undo last change") 

        # when triggered undo the editor 
        undo_action.triggered.connect(self.editor.undo) 

        # adding this to tool and menu bar 
        edit_toolbar.addAction(undo_action) 
        edit_menu.addAction(undo_action) 

        # redo action 
        redo_action = QAction("Redo", self) 
        redo_action.setStatusTip("Redo last change") 

        # when triggered redo the editor 
        redo_action.triggered.connect(self.editor.redo) 

        # adding this to menu and tool bar 
        edit_toolbar.addAction(redo_action) 
        edit_menu.addAction(redo_action) 

        # cut action 
        cut_action = QAction("Cut", self) 
        cut_action.setStatusTip("Cut selected text") 

        # when triggered cut the editor text 
        cut_action.triggered.connect(self.editor.cut) 

        # adding this to menu and tool bar 
        edit_toolbar.addAction(cut_action) 
        edit_menu.addAction(cut_action) 

        # copy action 
        copy_action = QAction("Copy", self) 
        copy_action.setStatusTip("Copy selected text") 

        # when triggered copy the editor text 
        copy_action.triggered.connect(self.editor.copy) 

        # adding this to menu and tool bar 
        edit_toolbar.addAction(copy_action) 
        edit_menu.addAction(copy_action) 

        # paste action 
        paste_action = QAction("Paste", self) 
        paste_action.setStatusTip("Paste from clipboard") 

        # when triggered paste the copied text 
        paste_action.triggered.connect(self.editor.paste) 

        # adding this to menu and tool bar 
        edit_toolbar.addAction(paste_action) 
        edit_menu.addAction(paste_action) 

        # select all action 
        select_action = QAction("Select all", self) 
        select_action.setStatusTip("Select all text") 

        # when this triggered select the whole text 
        select_action.triggered.connect(self.editor.selectAll) 

        # adding this to menu and tool bar 
        edit_toolbar.addAction(select_action) 
        edit_menu.addAction(select_action) 


        # wrap action 
        wrap_action = QAction("Wrap text to window", self) 
        wrap_action.setStatusTip("Check to wrap text to window") 

        # making it checkable 
        wrap_action.setCheckable(True) 

        # making it checked 
        wrap_action.setChecked(True) 

        # adding action 
        wrap_action.triggered.connect(self.edit_toggle_wrap) 

        # adding it to edit menu not to the tool bar 
        edit_menu.addAction(wrap_action) 

        # calling update title methpd 
        self.update_title() 

        # showing all the components 
        self.show() 

    # creating dialog critical method 
    # to show errors 
    def dialog_critical(self, s): 

        # creating a QMessageBox object 
        dlg = QMessageBox(self) 

        # setting text to the dlg 
        dlg.setText(s) 

        # setting icon to it 
        dlg.setIcon(QMessageBox.Critical) 

        # showing it 
        dlg.show() 

    # action called by file open action 
    def file_open(self): 

        # getting path and bool value 
        path, _ = QFileDialog.getOpenFileName(self, "Open file", "", 
                            "Text documents (*.txt);All files (*.*)") 

        # if path is true 
        if path: 
            # try opening path 
            try: 
                with open(path, 'rU') as f: 
                    # read the file 
                    text = f.read() 

            # if some error occured 
            except Exception as e: 

                # show error using critical method 
                self.dialog_critical(str(e)) 
            # else 
            else: 
                # update path value 
                self.path = path 

                # update the text 
                self.editor.setPlainText(text) 

                # update the title 
                self.update_title() 

    # action called by file save action 
    def file_save(self): 

        # if there is no save path 
        if self.path is None: 

            # call save as method 
            return self.file_saveas() 

        # else call save to path method 
        self._save_to_path(self.path) 

    # action called by save as action 
    def file_saveas(self): 

        # opening path 
        path, _ = QFileDialog.getSaveFileName(self, "Save file", "", 
                            "Text documents (*.txt);All files (*.*)") 

        # if dialog is cancelled i.e no path is selected 
        if not path: 
            # return this method 
            # i.e no action performed 
            return

        # else call save to path method 
        self._save_to_path(path) 

    # save to path method 
    def _save_to_path(self, path): 

        # get the text 
        text = self.editor.toPlainText() 

        # try catch block 
        try: 

            # opening file to write 
            with open(path, 'w') as f: 

                # write text in the file 
                f.write(text) 

        # if error occurs 
        except Exception as e: 

            # show error using critical 
            self.dialog_critical(str(e)) 

        # else do this 
        else: 
            # change path 
            self.path = path 
            # update the title 
            self.update_title() 

    # action called by print 
    def file_print(self): 

        # creating a QPrintDialog 
        dlg = QPrintDialog() 

        # if executed 
        if dlg.exec_(): 

            # print the text 
            self.editor.print_(dlg.printer()) 

    # update title method 
    def update_title(self): 

        # setting window title with prefix as file name 
        # suffix aas PyQt5 Notepad 
        self.setWindowTitle("%s - PyQt5 Notepad" %(os.path.basename(self.path) 
                                                if self.path else "Untitled")) 

    # action called by edit toggle 
    def edit_toggle_wrap(self): 

        # chaning line wrap mode 
        self.editor.setLineWrapMode(1 if self.editor.lineWrapMode() == 0 else 0 ) 


# drivers code 
if __name__ == '__main__': 

    # creating PyQt5 application 
    app = QApplication(sys.argv) 

    # setting application name 
    app.setApplicationName("PyQt5-Note") 

    # creating a main window object 
    window = MainWindow() 

    # loop 
    app.exec_()

Now if you run this python script by running the below command as shown below

python app.py