使用 PyQt5 创建记事本 - Python

在本文中，我们将了解如何使用 PyQt5 创建记事本。
记事本是一个通用文本编辑器，允许您创建、打开、编辑和读取纯文本文件。
PyQt5是跨平台的 GUI 工具包，一组用于 Qt v5 的Python绑定。由于该库提供的工具和简单性，人们可以非常轻松地开发交互式桌面应用程序。
使用此命令安装 PyQt5：

pip install PyQt5

GUI Implementation Steps :
1. Create a Vertical layout
2. Create a QPlainTextEdit object and add it to the layout
3. Create a container i.e QWidget object
4. Set this vertical layout to the container
5. Create a status bar to show status tips
6. Create file menu bar and add file actions below is how file menu bar will look like

7. Create an edit menu bar and add various edit action to it, below is how edit menu bar will look like

8. Create two toolbar for file and edit actions, below is how the toolbars will look like

Back End Implementation Steps :
1. Create a path variable and set it to None
2. Add actions to each of the file menu actions these are same of toolbar actions as both share same actions
3. Create a critical method that shows the passed value in the pop up, it is used to show if any error occurs during saving or opening file
4. Create update title method that changes the window title according to the name of the file
5. Inside the file open action, create a try-except block that try to open the file and then update the title and path
6. Inside the save action if path is none call the save as method else save file to the path
7. Inside the save as method save the file at the selected path by user
8. Inside the print action print the file using QPrintDialog object
9. Inside the edit toggle bar action set the line wrap mode of editor according to the checked state
10. Similarly set action for undo, redo, cut, copy, paste and select all using the QPlainTextEdit object built in functions

编程需要懂一点英语

下面是实现

Python3

# 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 window
        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 method
        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):
 
        # chaining 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_()

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