Chapter 4 — Add a QTableView¶
Now that you have a QMainWindow, you can include a centralWidget to your interface. Usually, a QWidget is used to display data in most data-driven applications. Use a table view to display your data.
The first step is to add a horizontal layout with just a QTableView. You can create a QTableView object and place it inside a QHBoxLayout. Once the QWidget is properly built, pass the object to the QMainWindow as its central widget.
Remember that a QTableView needs a model to display information. In this case, you can use a QAbstractTableModel instance.
You could also use the default item model that comes with a QTableWidget instead. QTableWidget is a convenience class that reduces your codebase considerably as you don’t need to implement a data model. However, it’s less flexible than a QTableView, as QTableWidget cannot be used with just any data. For more insight about Qt’s model-view framework, refer to the Model View Programming documentation.
Implementing the model for your QTableView, allows you to: — set the headers, — manipulate the formats of the cell values (remember we have UTC time and float numbers), — set style properties like text alignment, — and even set color properties for the cell or its content.
To subclass the QAbstractTable, you must reimplement its virtual methods, rowCount(), columnCount(), and data(). This way, you can ensure that the data is handled properly. In addition, reimplement the headerData() method to provide the header information to the view.
Here is a script that implements the CustomTableModel:
1 2from PySide2.QtCore import Qt, QAbstractTableModel, QModelIndex 3from PySide2.QtGui import QColor 4 5 6class CustomTableModel(QAbstractTableModel): 7 def __init__(self, data=None): 8 QAbstractTableModel.__init__(self) 9 self.load_data(data) 10 11 def load_data(self, data): 12 self.input_dates = data[0].values 13 self.input_magnitudes = data[1].values 14 15 self.column_count = 2 16 self.row_count = len(self.input_magnitudes) 17 18 def rowCount(self, parent=QModelIndex()): 19 return self.row_count 20 21 def columnCount(self, parent=QModelIndex()): 22 return self.column_count 23 24 def headerData(self, section, orientation, role): 25 if role != Qt.DisplayRole: 26 return None 27 if orientation == Qt.Horizontal: 28 return ("Date", "Magnitude")[section] 29 else: 30 return "<>".format(section) 31 32 def data(self, index, role=Qt.DisplayRole): 33 column = index.column() 34 row = index.row() 35 36 if role == Qt.DisplayRole: 37 if column == 0: 38 raw_date = self.input_dates[row] 39 date = "<>".format(raw_date.toPython()) 40 return date[:-3] 41 elif column == 1: 42 return " ".format(self.input_magnitudes[row]) 43 elif role == Qt.BackgroundRole: 44 return QColor(Qt.white) 45 elif role == Qt.TextAlignmentRole: 46 return Qt.AlignRight 47 48 return None 49
Now, create a QWidget that has a QTableView, and connect it to your CustomTableModel.
1 2from PySide2.QtWidgets import (QHBoxLayout, QHeaderView, QSizePolicy, 3 QTableView, QWidget) 4 5from table_model import CustomTableModel 6 7 8class Widget(QWidget): 9 def __init__(self, data): 10 QWidget.__init__(self) 11 12 # Getting the Model 13 self.model = CustomTableModel(data) 14 15 # Creating a QTableView 16 self.table_view = QTableView() 17 self.table_view.setModel(self.model) 18 19 # QTableView Headers 20 self.horizontal_header = self.table_view.horizontalHeader() 21 self.vertical_header = self.table_view.verticalHeader() 22 self.horizontal_header.setSectionResizeMode( 23 QHeaderView.ResizeToContents 24 ) 25 self.vertical_header.setSectionResizeMode( 26 QHeaderView.ResizeToContents 27 ) 28 self.horizontal_header.setStretchLastSection(True) 29 30 # QWidget Layout 31 self.main_layout = QHBoxLayout() 32 size = QSizePolicy(QSizePolicy.Preferred, QSizePolicy.Preferred) 33 34 ## Left layout 35 size.setHorizontalStretch(1) 36 self.table_view.setSizePolicy(size) 37 self.main_layout.addWidget(self.table_view) 38 39 # Set the layout to the QWidget 40 self.setLayout(self.main_layout) 41
You also need minor changes to the main_window.py and main.py from chapter 3 to include the Widget inside the MainWindow.
In the following snippets you’ll see those changes highlighted:
1 2from PySide2.QtCore import Slot 3from PySide2.QtGui import QKeySequence 4from PySide2.QtWidgets import QMainWindow, QAction 5 6 7class MainWindow(QMainWindow): 8 def __init__(self, widget): 9 QMainWindow.__init__(self) 10 self.setWindowTitle("Eartquakes information") 11 self.setCentralWidget(widget) 12 # Menu 13 self.menu = self.menuBar() 14 self.file_menu = self.menu.addMenu("File") 15 16 ## Exit QAction 17 exit_action = QAction("Exit", self) 18 exit_action.setShortcut(QKeySequence.Quit) 19 exit_action.triggered.connect(self.close) 20 21 self.file_menu.addAction(exit_action) 22 23 # Status Bar 24 self.status = self.statusBar() 25 self.status.showMessage("Data loaded and plotted") 26 27 # Window dimensions 28 geometry = qApp.desktop().availableGeometry(self) 29 self.setFixedSize(geometry.width() * 0.8, geometry.height() * 0.7) 30
1 2import sys 3import argparse 4import pandas as pd 5 6from PySide2.QtCore import QDateTime, QTimeZone 7from PySide2.QtWidgets import QApplication 8from main_window import MainWindow 9from main_widget import Widget 10 11 12def transform_date(utc, timezone=None): 13 utc_fmt = "yyyy-MM-ddTHH:mm:ss.zzzZ" 14 new_date = QDateTime().fromString(utc, utc_fmt) 15 if timezone: 16 new_date.setTimeZone(timezone) 17 return new_date 18 19 20def read_data(fname): 21 # Read the CSV content 22 df = pd.read_csv(fname) 23 24 # Remove wrong magnitudes 25 df = df.drop(df[df.mag 0].index) 26 magnitudes = df["mag"] 27 28 # My local timezone 29 timezone = QTimeZone(b"Europe/Berlin") 30 31 # Get timestamp transformed to our timezone 32 times = df["time"].apply(lambda x: transform_date(x, timezone)) 33 34 return times, magnitudes 35 36 37if __name__ == "__main__": 38 options = argparse.ArgumentParser() 39 options.add_argument("-f", "--file", type=str, required=True) 40 args = options.parse_args() 41 data = read_data(args.file) 42 43 # Qt Application 44 app = QApplication(sys.argv) 45 46 widget = Widget(data) 47 window = MainWindow(widget) 48 window.show() 49 50 sys.exit(app.exec_()) 51
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