[FIXED] How to use QPrinter and QPrintPreviewDialog

Issue

I want to preview, and then print, a report through a printer using PyQt. I tried the following code :

printer = QtGui.QPrinter()
doc  = QtGui.QTextDocument("testing")
dialog = QtGui.QPrintDialog(printer)
dialog.setModal(True)
dialog.setWindowTitle("printerrr")
pdialog = QtGui.QPrintPreviewDialog(printer)
pdialog.setWindowFlags(QtCore.Qt.Window)
pdialog.exec_()

How I can preview my report then print it?

Solution

Basic demo of Qt's print dialogs:

UPDATE:

An alternative solution to the ones given below is to use Qt WebEngine to render and print the documents. This allows a much greater range of document types to be supported in addition to HTML, such as PDFs, images, plain text, etc. The Printer class in the following example is based on the WebEngine Widgets PrintMe Example from the Qt docs.

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5 import QtPrintSupport, QtWebEngineWidgets


class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.viewer = QtWebEngineWidgets.QWebEngineView(self)
        self.viewer.settings().setAttribute(
            QtWebEngineWidgets.QWebEngineSettings.PluginsEnabled, True)
        self.viewer.settings().setAttribute(
            QtWebEngineWidgets.QWebEngineSettings.PdfViewerEnabled, True)
        self.buttonOpen = QtWidgets.QPushButton('Open', self)
        self.buttonOpen.clicked.connect(self.handleOpen)
        self.buttonPrint = QtWidgets.QPushButton('Print', self)
        self.buttonPrint.clicked.connect(self.handlePrint)
        self.buttonPreview = QtWidgets.QPushButton('Preview', self)
        self.buttonPreview.clicked.connect(self.handlePreview)
        layout = QtWidgets.QGridLayout(self)
        layout.addWidget(self.viewer, 0, 0, 1, 3)
        layout.addWidget(self.buttonOpen, 1, 0)
        layout.addWidget(self.buttonPrint, 1, 1)
        layout.addWidget(self.buttonPreview, 1, 2)
        self.printer = Printer(self.viewer.page(), self)

    def handleOpen(self):
        if path := QtWidgets.QFileDialog.getOpenFileName(self)[0]:
            self.viewer.load(QtCore.QUrl.fromLocalFile(path))

    def handlePrint(self):
        if self.viewer.url().isValid():
            self.printer.print()

    def handlePreview(self):
        if self.viewer.url().isValid():
            self.printer.preview()


class Printer(QtCore.QObject):
    def __init__(self, page, parent=None):
        super().__init__(parent)
        self._page = page
        self._printing = False

    def render(self, printer):
        loop = QtCore.QEventLoop()
        failed = False
        QtWidgets.QApplication.setOverrideCursor(QtCore.Qt.WaitCursor)
        def callback(result):
            nonlocal failed
            failed = not result
            QtWidgets.QApplication.restoreOverrideCursor()
            loop.quit()
        self._page.print(printer, callback)
        loop.exec()
        if failed:
            painter = QtGui.QPainter()
            if painter.begin(printer):
                font = painter.font()
                font.setPixelSize(20)
                painter.setFont(font)
                painter.drawText(QtCore.QPointF(10, 25),
                    'Could not generate print preview')
                painter.end()

    def preview(self):
        if not self._printing:
            self._printing = True
            printer = QtPrintSupport.QPrinter()
            printer.setResolution(300)
            dialog = QtPrintSupport.QPrintPreviewDialog(
                printer, self._page.view())
            dialog.paintRequested.connect(self.render)
            dialog.exec()
            dialog.deleteLater()
            self._printing = False

    def print(self):
        printer = QtPrintSupport.QPrinter(
            QtPrintSupport.QPrinter.HighResolution)
        dialog = QtPrintSupport.QPrintDialog(printer, self._page.view())
        if dialog.exec() == QtWidgets.QDialog.Accepted:
            self.render(printer)
        dialog.deleteLater()


if __name__ == '__main__':

    QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QtWidgets.QApplication(['Printing Demo'])
    window = Window()
    window.setGeometry(600, 100, 800, 600)
    window.show()
    app.exec()

---

Previous examples:

PyQt4:

    import sys, os
    from PyQt4 import QtGui, QtCore
    
    class Window(QtGui.QWidget):
        def __init__(self):
            super(Window, self).__init__()
            self.setWindowTitle('Document Printer')
            self.editor = QtGui.QTextEdit(self)
            self.editor.textChanged.connect(self.handleTextChanged)
            self.buttonOpen = QtGui.QPushButton('Open', self)
            self.buttonOpen.clicked.connect(self.handleOpen)
            self.buttonPrint = QtGui.QPushButton('Print', self)
            self.buttonPrint.clicked.connect(self.handlePrint)
            self.buttonPreview = QtGui.QPushButton('Preview', self)
            self.buttonPreview.clicked.connect(self.handlePreview)
            layout = QtGui.QGridLayout(self)
            layout.addWidget(self.editor, 0, 0, 1, 3)
            layout.addWidget(self.buttonOpen, 1, 0)
            layout.addWidget(self.buttonPrint, 1, 1)
            layout.addWidget(self.buttonPreview, 1, 2)
            self.handleTextChanged()
    
        def handleOpen(self):
            path = QtGui.QFileDialog.getOpenFileName(
                self, 'Open file', '',
                'HTML files (*.html);;Text files (*.txt)')
            if path:
                file = QtCore.QFile(path)
                if file.open(QtCore.QIODevice.ReadOnly):
                    stream = QtCore.QTextStream(file)
                    text = stream.readAll()
                    info = QtCore.QFileInfo(path)
                    if info.completeSuffix() == 'html':
                        self.editor.setHtml(text)
                    else:
                        self.editor.setPlainText(text)
                    file.close()
    
        def handlePrint(self):
            dialog = QtGui.QPrintDialog()
            if dialog.exec_() == QtGui.QDialog.Accepted:
                self.editor.document().print_(dialog.printer())
    
        def handlePreview(self):
            dialog = QtGui.QPrintPreviewDialog()
            dialog.paintRequested.connect(self.editor.print_)
            dialog.exec_()
    
        def handleTextChanged(self):
            enable = not self.editor.document().isEmpty()
            self.buttonPrint.setEnabled(enable)
            self.buttonPreview.setEnabled(enable)
    
    if __name__ == '__main__':
    
        app = QtGui.QApplication(sys.argv)
        window = Window()
        window.resize(640, 480)
        window.show()
        sys.exit(app.exec_())

PyQt5:

import sys, os
from PyQt5 import QtCore, QtWidgets, QtPrintSupport

class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.setWindowTitle('Document Printer')
        self.editor = QtWidgets.QTextEdit(self)
        self.editor.textChanged.connect(self.handleTextChanged)
        self.buttonOpen = QtWidgets.QPushButton('Open', self)
        self.buttonOpen.clicked.connect(self.handleOpen)
        self.buttonPrint = QtWidgets.QPushButton('Print', self)
        self.buttonPrint.clicked.connect(self.handlePrint)
        self.buttonPreview = QtWidgets.QPushButton('Preview', self)
        self.buttonPreview.clicked.connect(self.handlePreview)
        layout = QtWidgets.QGridLayout(self)
        layout.addWidget(self.editor, 0, 0, 1, 3)
        layout.addWidget(self.buttonOpen, 1, 0)
        layout.addWidget(self.buttonPrint, 1, 1)
        layout.addWidget(self.buttonPreview, 1, 2)
        self.handleTextChanged()

    def handleOpen(self):
        path = QtWidgets.QFileDialog.getOpenFileName(
            self, 'Open file', '',
            'HTML files (*.html);;Text files (*.txt)')[0]
        if path:
            file = QtCore.QFile(path)
            if file.open(QtCore.QIODevice.ReadOnly):
                stream = QtCore.QTextStream(file)
                text = stream.readAll()
                info = QtCore.QFileInfo(path)
                if info.completeSuffix() == 'html':
                    self.editor.setHtml(text)
                else:
                    self.editor.setPlainText(text)
                file.close()

    def handlePrint(self):
        dialog = QtPrintSupport.QPrintDialog()
        if dialog.exec_() == QtWidgets.QDialog.Accepted:
            self.editor.document().print_(dialog.printer())

    def handlePreview(self):
        dialog = QtPrintSupport.QPrintPreviewDialog()
        dialog.paintRequested.connect(self.editor.print_)
        dialog.exec_()

    def handleTextChanged(self):
        enable = not self.editor.document().isEmpty()
        self.buttonPrint.setEnabled(enable)
        self.buttonPreview.setEnabled(enable)

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.resize(640, 480)
    window.show()
    sys.exit(app.exec_())

To print-preview a graphics view, use its render method:

def handlePreview(self):
    # dialog = QtPrintSupport.QPrintPreviewDialog() # PyQt5
    dialog = QtGui.QPrintPreviewDialog()
    dialog.paintRequested.connect(self.handlePaintRequest)
    dialog.exec_()

def handlePaintRequest(self, printer):
    self.view.render(QtGui.QPainter(printer))

Answered By - ekhumoro