How can I "Print Preview" of document created by QTextDocument in PyQt5?

Question

Hello Experts!! I hope you are having great day. I am new in GUI programming specially PyQt5. I am practicing on simple GUI invoice application. In this application, I successfully generated the Invoice By QTextDocument. Now i want to add print dialogue and print preview option. I am having trouble in the code. This is saying

AttributeError: 'InvoiceForm' object has no attribute 'printpreviewDialog

As i am new, i am little bit confused in there. Could you please fix the code? That will help me a lot to study. Many Many Thanks. The code has given below:-

import sys
from PyQt5.QtCore import pyqtSignal, QSize, QSizeF, QDate
from PyQt5.QtGui import QTextDocument, QTextCursor, QFont
from PyQt5.QtPrintSupport import QPrinter, QPrintPreviewDialog
from PyQt5.QtWidgets import QWidget, QFormLayout, QLineEdit, QPlainTextEdit, QSpinBox, QDateEdit, QTableWidget, \
    QHeaderView, QPushButton, QHBoxLayout, QTextEdit, QApplication, QMainWindow

font= QFont('Arial',16)

class InvoiceForm(QWidget):
    submitted = pyqtSignal(dict)
    def __init__(self):
        super().__init__()
        self.setLayout(QFormLayout())
        self.inputs = dict()
        self.inputs['Customer Name'] = QLineEdit()
        self.inputs['Customer Address'] = QPlainTextEdit()
        self.inputs['Invoice Date'] = QDateEdit(date=QDate.currentDate(), calendarPopup=True)
        self.inputs['Days until Due'] = QSpinBox()
        for label, widget in self.inputs.items():
            self.layout().addRow(label, widget)

        self.line_items = QTableWidget(rowCount=10, columnCount=3)
        self.line_items.setHorizontalHeaderLabels(['Job', 'Rate', 'Hours'])
        self.line_items.horizontalHeader().setSectionResizeMode(QHeaderView.Stretch)
        self.layout().addRow(self.line_items)
        for row in range(self.line_items.rowCount()):
            for col in range(self.line_items.columnCount()):
                if col > 0:
                    w = QSpinBox()
                    self.line_items.setCellWidget(row, col, w)

        submit = QPushButton('Create Invoice', clicked=self.on_submit)
        print = QPushButton('Print Invoice', clicked=self.printpreviewDialog)
        self.layout().addRow(submit,print)

    def on_submit(self):
        data = {'c_name': self.inputs['Customer Name'].text(),
                'c_addr': self.inputs['Customer Address'].toPlainText(),
                'i_date': self.inputs['Invoice Date'].date().toString(),
                'i_due': self.inputs['Invoice Date'].date().addDays(self.inputs['Days until Due'].value()).toString(),
                'i_terms': '{} days'.format(self.inputs['Days until Due'].value()),
                'line_items': list()}

        for row in range(self.line_items.rowCount()):
            if not self.line_items.item(row, 0):
                continue
            job = self.line_items.item(row, 0).text()
            rate = self.line_items.cellWidget(row, 1).value()
            hours = self.line_items.cellWidget(row, 2).value()
            total = rate * hours
            row_data = [job, rate, hours, total]
            if any(row_data):
                data['line_items'].append(row_data)

        data['total_due'] = sum(x[3] for x in data['line_items'])
        self.submitted.emit(data)
        # remove everything else in this function below this point

class InvoiceView(QTextEdit):
    dpi = 72
    doc_width = 8.5 * dpi
    doc_height = 6 * dpi

    def __init__(self):
        super().__init__(readOnly=True)
        self.setFixedSize(QSize(self.doc_width, self.doc_height))

    def build_invoice(self, data):
        document = QTextDocument()
        self.setDocument(document)
        document.setPageSize(QSizeF(self.doc_width, self.doc_height))
        document.setDefaultFont(font)
        cursor = QTextCursor(document)
        cursor.insertText(f"Customer Name: {data['c_name']}\n")
        cursor.insertText(f"Customer Address: {data['c_addr']}\n")
        cursor.insertText(f"Date: {data['i_date']}\n")
        cursor.insertText(f"Total Due: {data['total_due']}\n")

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        central = QWidget()
        self.setCentralWidget(central)
        layout = QHBoxLayout(central)

        self.invoiceForm = InvoiceForm()
        layout.addWidget(self.invoiceForm)

        self.invoiceView = InvoiceView()
        layout.addWidget(self.invoiceView)
        # hide the widget right now...
        self.invoiceView.setVisible(False)

        self.invoiceForm.submitted.connect(self.showPreview)

    def showPreview(self, data):
        self.invoiceView.setVisible(True)
        self.invoiceView.build_invoice(data)

    def printpreviewDialog(self):
        printer = QPrinter(QPrinter.HighResolution)
        previewDialog = QPrintPreviewDialog(printer, self)
        previewDialog.paintRequested.connect(self.printPreview)
        previewDialog.exec_()

    def printPreview(self, printer):
        self.invoiceView.build_invoice.print_(printer)

def main():
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    app.exec_()

if __name__ == '__main__':
    main()

Answer 1

The main problem is that self.printpreviewDialog is a member of MainWindow, not of InvoiceForm, so you should connect the clicked signal from the main window instead.

Also note that you tried to use self.invoiceView.build_invoice.print_(), but this wouldn't work as you are not calling build_invoice, and even if you did, that function doesn't return anything.

You should use the self.invoiceView.document() instead, but you must ensure that the data has been built before.

class InvoiceForm(QWidget):
    submitted = pyqtSignal(dict)
    def __init__(self):
        # ...
        submit = QPushButton('Create Invoice', clicked=self.on_submit)
        # make the button a member of the instance instead of a local variable, 
        # so that we can connect from the main window instance
        self.printButton = QPushButton('Print Invoice')
        self.layout().addRow(submit, self.printButton)

# ...

class MainWindow(QMainWindow):
    def __init__(self):
        # ...
        self.invoiceForm.printButton.clicked.connect(self.printpreviewDialog)
    # ...

    def printPreview(self, printer):
        self.invoiceView.document().print_(printer)

Note: never, never use built-in functions and statements for variable names, like print.

Answer 2

Try it:

import sys
from PyQt5.QtCore import pyqtSignal, QSize, QSizeF, QDate
from PyQt5.QtGui import QTextDocument, QTextCursor, QFont
from PyQt5.QtPrintSupport import QPrinter, QPrintPreviewDialog
from PyQt5.QtWidgets import (QWidget, QFormLayout, QLineEdit, QPlainTextEdit, 
    QSpinBox, QDateEdit, QTableWidget, QHeaderView, QPushButton, QHBoxLayout, 
    QTextEdit, QApplication, QMainWindow)


font = QFont('Arial',16)


class InvoiceForm(QWidget):
    submitted = pyqtSignal(dict)
    
    def __init__(self, parent=None):                                        # + parent=None
        super().__init__(parent)                                            # + parent
        self.setLayout(QFormLayout())
        self.inputs = dict()
        self.inputs['Customer Name'] = QLineEdit()
        self.inputs['Customer Address'] = QPlainTextEdit()
        self.inputs['Invoice Date'] = QDateEdit(date=QDate.currentDate(), calendarPopup=True)
        self.inputs['Days until Due'] = QSpinBox()
        for label, widget in self.inputs.items():
            self.layout().addRow(label, widget)

        self.line_items = QTableWidget(rowCount=10, columnCount=3)
        self.line_items.setHorizontalHeaderLabels(['Job', 'Rate', 'Hours'])
        self.line_items.horizontalHeader().setSectionResizeMode(QHeaderView.Stretch)
        self.layout().addRow(self.line_items)
        for row in range(self.line_items.rowCount()):
            for col in range(self.line_items.columnCount()):
                if col > 0:
                    w = QSpinBox()
                    self.line_items.setCellWidget(row, col, w)

        submit = QPushButton('Create Invoice', clicked=self.on_submit)
        
# +     vvvvvv                                        vvvvvvvvvvvvv 
        _print = QPushButton('Print Invoice', clicked=self.window().printpreviewDialog)  # + _print, + self.window()
        self.layout().addRow(submit, _print)                                             # + _print

    def on_submit(self):
        data = {'c_name': self.inputs['Customer Name'].text(),
                'c_addr': self.inputs['Customer Address'].toPlainText(),
                'i_date': self.inputs['Invoice Date'].date().toString(),
                'i_due': self.inputs['Invoice Date'].date().addDays(self.inputs['Days until Due'].value()).toString(),
                'i_terms': '{} days'.format(self.inputs['Days until Due'].value()),
                'line_items': list()}

        for row in range(self.line_items.rowCount()):
            if not self.line_items.item(row, 0):
                continue
            job = self.line_items.item(row, 0).text()
            rate = self.line_items.cellWidget(row, 1).value()
            hours = self.line_items.cellWidget(row, 2).value()
            total = rate * hours
            row_data = [job, rate, hours, total]
            if any(row_data):
                data['line_items'].append(row_data)

        data['total_due'] = sum(x[3] for x in data['line_items'])
        self.submitted.emit(data)
        # remove everything else in this function below this point
# +
        return data                                                            # +++
        

class InvoiceView(QTextEdit):
    dpi = 72
    doc_width = 8.5 * dpi
    doc_height = 6 * dpi

    def __init__(self):
        super().__init__(readOnly=True)
        self.setFixedSize(QSize(self.doc_width, self.doc_height))

    def build_invoice(self, data):
        document = QTextDocument()
        self.setDocument(document)
        document.setPageSize(QSizeF(self.doc_width, self.doc_height))
        document.setDefaultFont(font)
        cursor = QTextCursor(document)
        cursor.insertText(f"Customer Name: {data['c_name']}\n")
        cursor.insertText(f"Customer Address: {data['c_addr']}\n")
        cursor.insertText(f"Date: {data['i_date']}\n")
        cursor.insertText(f"Total Due: {data['total_due']}\n")
# +        
        return document                                                         # +++
        

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        central = QWidget()
        self.setCentralWidget(central)
        layout = QHBoxLayout(central)
# +                                    vvvv
        self.invoiceForm = InvoiceForm(self)                                    # + self
        
        layout.addWidget(self.invoiceForm)
        self.invoiceView = InvoiceView()
        layout.addWidget(self.invoiceView)
        # hide the widget right now...
        self.invoiceView.setVisible(False)
        self.invoiceForm.submitted.connect(self.showPreview)

    def showPreview(self, data):
        self.invoiceView.setVisible(True)
        self.invoiceView.build_invoice(data)

# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    def printpreviewDialog(self):
        previewDialog = QPrintPreviewDialog()
        previewDialog.paintRequested.connect(self.printPreview)  
        previewDialog.exec_()

    def printPreview(self, printer):
#        self.invoiceView.build_invoice.print_(printer)        
        data = self.invoiceForm.on_submit()
        document = self.invoiceView.build_invoice(data)
        document.print_(printer)
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


def main():
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    app.exec_()

if __name__ == '__main__':
    main()