pythonqmlpyside2
Expose a looped changing python variable to QML
I am trying to take a python variable and use it within QML. My implementation is creating a button, which when clicked, will take data generated from my program and append the float values to x and y of a line series. Any suggestions?
Here is a little code from my program that will replicate my issue:
# ======================================================================== #
from math import exp
class ErrorFunction:
def firstPoint(self, param):
if param < 0:
return -self.firstPoint(-param)
else:
p = 0.47047
a = [0.3480242, -0.0958798, 0.7478556]
t = 1.0 / (1.0 + p * param)
return 1 - t * (a[0] + t * (a[1] + t * a[2])) * exp(-(param ** 2))
def successivePoint(self, param):
return 1 - self.firstPoint(param)
# ======================================================================== #
# ======================================================================== #
import os
import sys
from PySide2.QtQml import QQmlApplicationEngine
from PySide2.QtWidgets import QApplication
from ErrorFunction import ErrorFunction
class ErrorFunctionRunnable:
def __init__(self):
errorfunction = ErrorFunction()
n = 100
errorPoints = [(0, 0)] * n
for i in range(n):
x = i * 0.1 - 5.0
errorPoints[i] = (errorfunction.firstPoint(x), errorfunction.successivePoint(x))
print(errorPoints[i])
if __name__ == "__main__":
os.environ["QT_QUICK_CONTROLS_STYLE"] = "Material"
app = QApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.load(os.path.join(os.path.dirname(__file__), "gui.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec_())
# ======================================================================== #
// ======================================================================== #
import QtQuick 2.0
import QtQuick.Controls 2.5
import QtQuick.Controls.Material 2.3
import QtCharts 2.3
ApplicationWindow {
id: applicationWindow
visible: true
width: 720
height: 780
title: qsTr("QML Test")
Material.background: Material.color(Material.Grey, Material.Shade900)
GroupBox {
id: groupBox
width: 114
anchors.top: parent.top
anchors.topMargin: 0
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
anchors.left: parent.left
anchors.leftMargin: 0
Button {
id: button
x: 8
y: 0
width: 74
height: 48
text: qsTr("E_r")
font.pointSize: 10
Material.foreground: Material.color(Material.Grey, Material.Shade100)
Material.background: Material.color(Material.Grey, Material.Shade800)
onClicked: {
line.removeAllSeries()
/*
Run the "ErrorFunctionRunnable" init function to generate "errorPoints"
*/
}
}
}
GroupBox {
id: groupBox2
anchors.right: parent.right
anchors.rightMargin: 0
anchors.top: parent.top
anchors.topMargin: 0
anchors.left: parent.left
anchors.leftMargin: 114
anchors.bottom: parent.bottom
anchors.bottomMargin: 75
ChartView {
id: line
dropShadowEnabled: false
anchors.left: parent.left
anchors.leftMargin: 0
anchors.top: parent.top
anchors.topMargin: 0
anchors.right: parent.right
anchors.rightMargin: 0
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
theme: ChartView.ChartThemeDark
antialiasing: true
backgroundColor: Material.color(Material.Grey, Material.Shade900)
LineSeries {
name: "Marshak Wave"
/*
Update the line series with the points from "errorPoints"
*/
}
}
}
GroupBox {
id: groupBox1
y: 704
height: 76
anchors.right: parent.right
anchors.rightMargin: 0
anchors.left: parent.left
anchors.leftMargin: 114
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
}
}
// ======================================================================== #
Solution
A possible solution is to create a QObject that exposes the QPointF list through a method to QML, in addition the limits of the axes must be updated as shown below:
import math
import os
import sys
from PySide2.QtCore import QObject, QPointF, Slot
from PySide2.QtQml import QQmlApplicationEngine
from PySide2.QtWidgets import QApplication
class ErrorFunction:
def firstPoint(self, param):
if param < 0:
return -self.firstPoint(-param)
else:
p = 0.47047
a = [0.3480242, -0.0958798, 0.7478556]
t = 1.0 / (1.0 + p * param)
return 1 - t * (a[0] + t * (a[1] + t * a[2])) * math.exp(-(param ** 2))
def successivePoint(self, param):
return 1 - self.firstPoint(param)
class Bridge(QObject):
@Slot(result="QVariantList")
def produce(self):
f = ErrorFunction()
values = []
n = 100
for i in range(n):
x = i * 0.1 - 5.0
p = QPointF(f.firstPoint(x), f.successivePoint(x))
values.append(p)
return values
if __name__ == "__main__":
os.environ["QT_QUICK_CONTROLS_STYLE"] = "Material"
app = QApplication(sys.argv)
bridge = Bridge()
engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty("bridge", bridge)
engine.load(os.path.join(os.path.dirname(__file__), "gui.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec_())
import QtQuick 2.0
import QtQuick.Controls 2.5
import QtQuick.Controls.Material 2.3
import QtCharts 2.3
ApplicationWindow {
id: applicationWindow
visible: true
width: 720
height: 780
title: qsTr("QML Test")
Material.background: Material.color(Material.Grey, Material.Shade900)
GroupBox {
id: groupBox
width: 114
anchors.top: parent.top
anchors.topMargin: 0
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
anchors.left: parent.left
anchors.leftMargin: 0
Button {
id: button
x: 8
y: 0
width: 74
height: 48
text: qsTr("E_r")
font.pointSize: 10
Material.foreground: Material.color(Material.Grey, Material.Shade100)
Material.background: Material.color(Material.Grey, Material.Shade800)
onClicked: {
line.removePoints(0, line.count)
var x_min = line.axisX.min
var x_max = line.axisX.max
var y_min = line.axisY.min
var y_max = line.axisY.max
var values = bridge.produce()
for(var i in values){
line.append(values[i].x, values[i].y)
x_min = Math.min(x_min, values[i].x)
x_max = Math.max(x_max, values[i].x)
y_min = Math.min(y_min, values[i].y)
y_max = Math.max(y_max, values[i].y)
}
line.axisX.min = x_min
line.axisX.max = x_max
line.axisY.min = y_min
line.axisY.max = y_max
}
}
}
GroupBox {
id: groupBox2
anchors.fill: parent
anchors.rightMargin: 0
anchors.topMargin: 0
anchors.leftMargin: 114
anchors.bottomMargin: 75
ChartView {
id: view
dropShadowEnabled: false
anchors.fill: parent
anchors.margins: 0
theme: ChartView.ChartThemeDark
antialiasing: true
backgroundColor: Material.color(Material.Grey, Material.Shade900)
LineSeries {
id: line
name: "Marshak Wave"
}
}
}
GroupBox {
id: groupBox1
y: 704
height: 76
anchors.right: parent.right
anchors.rightMargin: 0
anchors.left: parent.left
anchors.leftMargin: 114
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
}
}
The disadvantage is the for-loop in QML if the data has many elements, a possible optimization is to use the replace method but it is not accessible in QML so the element has to be exported to python:
import math
import os
import sys
from PySide2.QtCore import QObject, QPointF, Slot
from PySide2.QtQml import QQmlApplicationEngine
from PySide2.QtWidgets import QApplication
from PySide2.QtCharts import QtCharts
class ErrorFunction:
def firstPoint(self, param):
if param < 0:
return -self.firstPoint(-param)
else:
p = 0.47047
a = [0.3480242, -0.0958798, 0.7478556]
t = 1.0 / (1.0 + p * param)
return 1 - t * (a[0] + t * (a[1] + t * a[2])) * math.exp(-(param ** 2))
def successivePoint(self, param):
return 1 - self.firstPoint(param)
class Bridge(QObject):
@Slot(QtCharts.QAbstractSeries)
def fill(self, series):
axis_x = series.property("axisX")
axis_y = series.property("axisY")
xmin = axis_x.min()
xmax = axis_x.max()
ymin = axis_y.min()
ymax = axis_y.max()
f = ErrorFunction()
values = []
n = 100
for i in range(n):
x = i * 0.1 - 5.0
xi = f.firstPoint(x)
yi = f.successivePoint(x)
p = QPointF(xi, yi)
xmin = min(xmin, xi)
xmax = max(xmax, xi)
ymin = min(ymin, yi)
ymax = max(ymax, yi)
values.append(p)
series.replace(values)
axis_x.setMin(xmin)
axis_x.setMax(xmax)
axis_y.setMin(ymin)
axis_y.setMax(ymax)
if __name__ == "__main__":
os.environ["QT_QUICK_CONTROLS_STYLE"] = "Material"
app = QApplication(sys.argv)
bridge = Bridge()
engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty("bridge", bridge)
engine.load(os.path.join(os.path.dirname(__file__), "gui.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec_())
import QtQuick 2.0
import QtQuick.Controls 2.5
import QtQuick.Controls.Material 2.3
import QtCharts 2.3
ApplicationWindow {
id: applicationWindow
visible: true
width: 720
height: 780
title: qsTr("QML Test")
Material.background: Material.color(Material.Grey, Material.Shade900)
GroupBox {
id: groupBox
width: 114
anchors.top: parent.top
anchors.topMargin: 0
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
anchors.left: parent.left
anchors.leftMargin: 0
Button {
id: button
x: 8
y: 0
width: 74
height: 48
text: qsTr("E_r")
font.pointSize: 10
Material.foreground: Material.color(Material.Grey, Material.Shade100)
Material.background: Material.color(Material.Grey, Material.Shade800)
onClicked: {
bridge.fill(line)
}
}
}
GroupBox {
id: groupBox2
anchors.fill: parent
anchors.rightMargin: 0
anchors.topMargin: 0
anchors.leftMargin: 114
anchors.bottomMargin: 75
ChartView {
id: view
dropShadowEnabled: false
anchors.fill: parent
anchors.margins: 0
theme: ChartView.ChartThemeDark
antialiasing: true
backgroundColor: Material.color(Material.Grey, Material.Shade900)
LineSeries {
id: line
name: "Marshak Wave"
}
}
}
GroupBox {
id: groupBox1
y: 704
height: 76
anchors.right: parent.right
anchors.rightMargin: 0
anchors.left: parent.left
anchors.leftMargin: 114
anchors.bottom: parent.bottom
anchors.bottomMargin: 0
}
}
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