Variables across classes to scale plot in PyQt GUI

Question

I'm making a GUI which is to have a couple user input boxes and a plot which will use factors in the input boxes to scale data. The GUI will need an apply button and an export button. I am using PyQt5 for the GUI and Matplotlib for the plotting. My approach has been to create separate QWidgets for the plot and the input boxes and tie them together in a third QMainWindow.

I have the GUI appearing correctly

How can I get the apply button to send the 3 variables across to the main class and to the plotting class? Would it be possible to have all of this happen within one class to simplify how my variables will work?

import sys
import matplotlib
matplotlib.use("Qt5Agg")
from PyQt5 import QtCore
from PyQt5.QtCore import pyqtSlot, pyqtSignal, QObject
from PyQt5.QtWidgets import *
from numpy import arange, sin, pi
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure

class AppForm(QWidget):

    def __init__(self):
        # Initialize the object as a QWidget and
        # set its title and minimum width
        QWidget.__init__(self)
        self.setWindowTitle('Input')
        self.setMinimumWidth(400)

        # Create the QVBoxLayout that lays out the whole form
        self.layout = QVBoxLayout()

        # Create the form layout that manages the labeled controls
        self.form_layout = QFormLayout()

        self.aFactor = QLineEdit(self)
        self.mFactor = QLineEdit(self)
        self.cZone = QLineEdit(self)

        self.form_layout.addRow('AFactor', self.aFactor)
        self.form_layout.addRow('MFactor', self.mFactor)
        self.form_layout.addRow('CZone', self.cZone)

        self.layout.addLayout(self.form_layout)
        self.button_box = QHBoxLayout()
        self.button_box.addStretch(1)

        self.apply_button = QPushButton("Apply", self)
        self.output_button = QPushButton("Output", self)

        self.button_box.addWidget(self.apply_button)
        self.button_box.addWidget(self.output_button)
        self.layout.addLayout(self.button_box)
        self.setLayout(self.layout)

        self.apply_button.clicked.connect(self.applyButton)

    def applyButton(self):
        self.af = self.aFactor
        self.mf = self.mFactor
        self.cz = self.cZone

        print self.af.text(), self.mf.text(), self.cz.text()

class MyMplCanvas(FigureCanvas):
    """Ultimately, this is a QWidget (as well as a FigureCanvasAgg, etc.)."""
    def __init__(self, parent=None, width=5, height=4, dpi=100, title='title'):
        self.title = title
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = fig.add_subplot(111)
        fig.suptitle(title)

        # We want the axes cleared every time plot() is called
        self.axes.hold(False)

        self.compute_initial_figure()


        FigureCanvas.__init__(self, fig)
        self.setParent(parent)

        FigureCanvas.setSizePolicy(self,
                QSizePolicy.Expanding,
                QSizePolicy.Expanding)
        FigureCanvas.updateGeometry(self)

    def compute_initial_figure(self):
        pass


class MyStaticMplCanvas(MyMplCanvas):
    """Simple canvas with a sine plot."""
    def compute_initial_figure(self):
        t = arange(0.0, 3.0, 0.01)
        s = sin(2*pi*t)
        self.axes.plot(t, s)
        self.axes.set_ylabel('label1')
        self.axes.set_xlabel('label')
        self.axes.grid(True)



class ApplicationWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        self.setAttribute(QtCore.Qt.WA_DeleteOnClose)
        self.setWindowTitle("application main window")
        self.setMinimumWidth(800)
        self.setMinimumHeight(600)

        self.file_menu = QMenu('&File', self)
        self.file_menu.addAction('&Quit', self.fileQuit,
                QtCore.Qt.CTRL + QtCore.Qt.Key_Q)
        self.menuBar().addMenu(self.file_menu)

        self.help_menu = QMenu('&Help', self)
        self.menuBar().addSeparator()
        self.menuBar().addMenu(self.help_menu)

        self.help_menu.addAction('&About', self.about)

        self.main_widget = QWidget(self)

        l = QVBoxLayout(self.main_widget)
        form = AppForm()
        sc = MyStaticMplCanvas(self.main_widget, width=5, height=4, dpi=100, title='Title 1')
        l.addWidget(form)
        l.addWidget(sc)

        self.main_widget.setFocus()
        self.setCentralWidget(self.main_widget)

        #self.statusBar().showMessage("Cool", 2000

    def fileQuit(self):
        self.close()

    def closeEvent(self, ce):
        self.fileQuit()

    def about(self):
        QMessageBox.about(self, "About",)


if __name__ == '__main__':
    app = QApplication(sys.argv)

    aw = ApplicationWindow()
    aw.setWindowTitle("PyQt5 Matplot Example")
    aw.show()
    #sys.exit(qApp.exec_())
    app.exec_()

Answer 1

There are several options here:

(a) Peform the work in the main class: Instead of connecting the button in the AppForm to a method in AppForm , do the same in the ApplicationWindow .

self.form = AppForm()
self.sc = MyStaticMplCanvas(....)
self.form.apply_button.clicked.connect(self.applyButton)

def applyButton(self):
    tx = self.form.aFactor.text()
    # do something with tx
    # e.g. call a method from MplCanvas
    self.sc.someMethod(tx)

(b) Use signals and slots: Create a signla in AppForm . Once the button is clicked, applyButton may emit this signal with the relevant content. In ApplicationWindow connect that signal to a method which can use the supplied data in some way. You can also connect it directly to a method of MplCanvas .

class AppForm(QWidget):
    mysignal = pyqtSignal(object)
    def __init__(self):
        ....
        self.apply_button.clicked.connect(self.applyButton)

    def applyButton(self):
        self.mysignalemit((self.aFactor.text(),self.mFactor.text(), self.cZone()) )

class ApplicationWindow(QMainWindow):
    def __init__(self):
        ....
        self.form = AppForm()
        self.sc = MyStaticMplCanvas(....)
        self.form.mysignal.connect(self.useButtonResults)
        self.form.mysignal.connect(self.sc.someMethod)

    def useButtonResults(self, obj):
        a,b,c = obj
        # do something with a, b, c

(c) Use a single class to do everything: Just put everything in a single class and do whatever you like.