Qt - Python Quick Reference
In this article we build a quick reference for much of the Qt Framework!
- One can spend a LOT of time finding these code example references that actually work, and are specific to the various widgets of Qt in the Python environment.
- This is a golden quick reference!
[Python Setting up Qt Environment]
[Setting venv]
python -m venv venv
[Activating venv]
source bin activate
[Installing modules]
python -m pip install module
[Qt Button] - Quick Reference
#import example
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget, QPushButton, QFileDialog, QGraphicsScene, QGraphicsPixmapItem, QGraphicsView, QMessageBox, QToolTip
Creation Example
#region SubRegion [button_1]
self.button_1 = QtWidgets.QPushButton(self.centralwidget)
self.button_1.setObjectName("button_1")
self.button_1.setText("Find Troughs")
self.button_1.clicked.connect(self.button_1ClickedfindTroughs)
self.horizontalLayout.addWidget(self.button_1)
#endregion
Set Size (Minimum / Maximum)
self.pushButton.setMinimumSize(QtCore.QSize(20, 20))
self.pushButton.setMaximumSize(QtCore.QSize(20, 20))
Clicked Handler
self.pushButton.clicked.connect(self.pushButtonAction)
Set Rounded Corners
button.setStyleSheet("border-radius : 50; border : 2px solid black")
Change Background Color
self.pushButton.setStyleSheet("background-color: red")
Set Geometry
button.setGeometry(200, 150, 100, 30)
Set Button Icon
button.setIcon(QIcon('logo.png'))
[Qt Slider] - Quick Reference
#import example
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget, QPushButton, QFileDialog, QGraphicsScene, QGraphicsPixmapItem, QGraphicsView, QMessageBox, QToolTip, QSlider
Creation Example
#region SubRegion [slider_3neigh]
self.slider_3 = QtWidgets.QSlider(self.centralwidget)
self.slider_3.setOrientation(QtCore.Qt.Horizontal)
self.slider_3.setMinimumSize(QtCore.QSize(120, 20))
self.slider_3.setMaximumSize(QtCore.QSize(120, 20))
self.slider_3.setMinimum(5)
self.slider_3.setMaximum(1000)
self.slider_3.valueChanged.connect(self.slider_3Change)
self.slider_3.setObjectName("slider_3")
self.horizontalLayout.addWidget(self.slider_3)
#endregion
Set Size (Minimum / Maximum)
self.slider_3.setMinimumSize(QtCore.QSize(120, 20))
self.slider_3.setMaximumSize(QtCore.QSize(120, 20))
Value Changed Handler
self.slider_3.valueChanged.connect(self.slider_3Change)
# Inside the event handler
def slider_2Change(self, event):
mvalue = event # Will hold the number
[Qt Label] - Quick Reference
#import example
from PyQt5.QtWidgets import QLabel
Creation Example
"#region SubRegion [label_slider_1]
self.label_1 = QtWidgets.QLabel(self.centralwidget)
self.label_1.setObjectName("label_1")
self.label_1.setText('smoothAvg: 1')
self.horizontalLayout.addWidget(self.label_1)
#endregion
Set Size (Minimum / Maximum)
self.label_1.setMinimumSize(QtCore.QSize(120, 20))
self.label_1.setMaximumSize(QtCore.QSize(120, 20))
Set Text
self.label_1.setText("Label Text")
[Qt File Menu] - Quick Reference
#import example
from PyQt5.QtWidgets import QMenuBar, QFileDialog
Part 1: Defining you Need a Menu Bar Itself
self.menubar = QtWidgets.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 23))
self.menubar.setObjectName("menubar")
Part 2: Defining the The Main Menu 'File' - Two are shown here
self.menuFile = QtWidgets.QMenu(self.menubar)
self.menuFile.setObjectName("menuFile")
self.menuFiletwo = QtWidgets.QMenu(self.menubar)
self.menuFiletwo.setObjectName("menuFiletwo")
self.menuFile.setTitle(_translate("MainWindow", "File"))
self.menuFiletwo.setTitle(_translate("MainWindow", "Filetwo"
Part 3: Defining Actions 'Open' under the File Menu main options
self.actionOpen = QtWidgets.QAction(MainWindow)
self.actionOpen.setObjectName("actionOpen")
self.actionOpen.triggered.connect(self.menu_Open)
self.menuFile.addAction(self.actionOpen)
self.menubar.addAction(self.menuFile.menuAction())
self.menuFiletwo.addAction(self.actionOpen)
self.menubar.addAction(self.menuFiletwo.menuAction())
[Qt File Dialog] - Quick Reference
#import example
from PyQt5.QtWidgets import QFileDialog
File Dialog Example
self.fdialog = QtWidgets.QFileDialog()
self.fdialog.setFileMode(QtWidgets.QFileDialog.ExistingFile)
if self.fdialog.exec_():
self.filename = str(self.fdialog.selectedFiles()[0])
[Qt QtWidgets.QGraphicsView] - Quick Reference
Part 1: Main Creation Example (Overriding the base class)
self.Draw_View = Draw_draw(self.gridLayoutWidget_2)
self.Draw_View.setObjectName("graphicsView")
self.Draw_View.setMouseTracking(True)
self.gridLayout_2.addWidget(self.Draw_View, 0, 0, 1, 1)
Part 2: Creating a override Draw Class
class Draw_draw(QtWidgets.QGraphicsView):
def __init__(self, parent):
super(Mfft_draw, self).__init__(parent)
Part 3: Overriding the Draw Function itself (7 parts)
Part 3a: Defining a Image (Must Pre-fill)
self.image = QImage(self.width, self.height, QImage.Format_RGB32)
self.image.fill(QColor(220,220,220))
Part 3b: Assigning a QPainter to Draw on the Image
qpainter = QPainter(self.image)
qpainter.setBrush(QColor(255,255,255))
qpainter.setPen(QColor(20,20,20))
Part 3c-1: Draw Line Example
qpainter.drawLine(x1, y1, x2, y2)
Part 3c-2: Draw Rectangle Example
qpainter.drawRect(x1, y1, w, h)
Part 4: Finish QPainter
qpainter.end()
Part 5: Create Pixmap
self.pixmap = QPixmap.fromImage(self.image)
Part 6: Create PixmapItem
self.pixmapItem = QGraphicsPixmapItem(self.pixmap)
Part 7: Create a Scene - Set Self to point to it
scene = QGraphicsScene()
scene.clear()
scene.addItem(self.pixmapItem)
[Qt QtWidgets.QGraphicsView] - Scaling Quick Reference
This scaling code will work for any QImage that is being hosted by the override class
def resizeEvent(self, event):
self.width = event.size().width()
self.height = event.size().height()
self.draw()
def wheelEvent(self, event):
#region Reference Scene Scaling Example
zoom_factor = 1.15
if event.angleDelta().y() > 0:
self.scale(zoom_factor, zoom_factor)
else:
self.scale(1 / zoom_factor, 1 / zoom_factor)
def mousePressEvent(self, event):
if event.button() == Qt.LeftButton:
self.startPos = event.pos()
print(f"Setting self.startPos: {self.startPos}")
self.click_mode = 'MOVE'
else:
self.startPos = None
# Override the mouse press event for custom behavior
epos = event.pos()
scene_pos = self.mapToScene(event.pos())
super().mousePressEvent(event)
def mouseMoveEvent(self, event):
if self.startPos is not None:
# compute the difference between the current cursor position and the
# previous saved origin point
delta = self.startPos - event.pos()
# get the current transformation (which is a matrix that includes the
# scaling ratios
transform = self.transform()
# m11 refers to the horizontal scale, m22 to the vertical scale;
# divide the delta by their corresponding ratio
deltaX = delta.x() / transform.m11()
deltaY = delta.y() / transform.m22()
# translate the current sceneRect by the delta
self.setSceneRect(self.sceneRect().translated(deltaX, deltaY))
# update the new origin point to the current position
self.startPos = event.pos()
def mouseReleaseEvent(self, event):
self.startPos = None
- It needs understanding that you typically create a QAbstractTableModel which is viewed through a TableView
[Qt QAbstractTableModel] - QAbstract Table Model
This model is pretty typical for most QAbstractTableModel Views
#region SubRegion [TableModel]
class TableModel(QAbstractTableModel):
def __init__(self, data=None):
super().__init__()
if data is not None:
self.load_data(data)
def load_data(self, data):
if data is not None:
self.data = data
self.column_count = len(self.data[0])
self.row_count = len(self.data)
else:
self.data = []
self.column_count = 0
self.row_count = 0
def rowCount(self, parent=QModelIndex()):
return len(self.data)
def columnCount(self, parent=QModelIndex()):
return len(self.data[0])
def headerData(self, section, orientation, role):
if role != Qt.DisplayRole:
return None
if orientation == Qt.Horizontal:
return ("Col A", "Col B", "Difference")[section]
else:
return f"{section}"
def setData(self, data):
self.load_data(data)
def data(self, index, role=Qt.DisplayRole):
column = index.column()
row = index.row()
if role == Qt.DisplayRole:
if 0 <= column <= 2:
return str(self.data[row][column])
elif role == Qt.BackgroundRole:
return QColor(Qt.white)
elif role == Qt.TextAlignmentRole:
return Qt.AlignRight
return None
#endregion
- Once you have that - it is simply a matter of pointing it to a table view
[Qt QtWidgets.QTableView] - QTableView
#region SubRegion [tableWidget]
self.tableWidget = TableViewAny(parent=self.horizontalLayoutWidget)
self.tableWidget.setObjectName("tableWidget")
self.tableWidget.clicked.connect(self.tableWidgetClicked)
self.horizontalLayout.addWidget(self.tableWidget)
#endregion
- Handling Table Selections (Selection Model)
- You cannot hook to .mouseReleaseEvent it must be an inheritance override:
[Qt QtWidgets.QTableView] - Selection Model
class TableViewAny(QtWidgets.QTableView):
def __init__(self, parent=None):
super().__init__(parent)
def setData(self, data):
pass
def setModel(self, in_Model):
super().setModel(in_Model)
def mouseReleaseEvent(self, event):
a = self.selectedIndexes()
if self.selectionModel():
selected_rows = self.selectionModel().selectedRows()
selected_cells = self.selectionModel().selectedIndexes()
for item in selected_cells:
row = item.row()
col = item.column()
data = item.data(QtCore.Qt.DisplayRole)
More to follow as required!
