PyQt5 Matplotlib figure- update with user input

Question

I am new to GUI devolopment and trying to develop an app using pyqt5 in python. I want it to show a figure and a few user widgets to update the figure through user input. Below is the code:

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QSizePolicy, QWidget, QComboBox, QLabel, QRadioButton, QCheckBox, QGridLayout, QLineEdit
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
import matplotlib as mpl
import matplotlib.pyplot as plt
import random
import numpy as np

class App(QWidget):

    def __init__(self):
        super().__init__()
        self.left = 0
        self.top = 800
        self.title = 'Chip2 Torque Data'
        self.width = 800
        self.height =800
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        l = QGridLayout(self)
        #hbox = MyMplCanvas(self.main_widget, width=50, height=40, dpi=100)
        self.figure = plt.figure(figsize=(15,5))    
        self.canvas = FigureCanvas(self.figure)   
        l.addWidget(self.canvas, 0,0,9,(100-4))

        xselect=QRadioButton("X",self)
        xselect.setChecked(True)

        zselect=QRadioButton("Z",self)

        sselect=QRadioButton("SP1",self)
        l.addWidget(xselect,0,(100-1))
        l.addWidget(zselect,0,(100-2))
        l.addWidget(sselect,0,(100-3))


        pass_list=QComboBox(self)
        pass_list.addItems(sheets_idealcut)
        l.addWidget(pass_list,1,(100-3),1,3)

        rawdata_check=QCheckBox("Raw Data",self)
        rawdata_check.setChecked(True)
        l.addWidget(rawdata_check,2,(100-3),1,3)

        mvgavg_check=QCheckBox("Moving average",self)
        mvgavg_check.setChecked(True)

        mvgstd_check=QCheckBox("Moving stdev",self)
        mvgstd_check.setChecked(True)
        l.addWidget(mvgavg_check,3,(100-3),1,3)
        l.addWidget(mvgstd_check,4,(100-3),1,3)


        xlim_left=QLineEdit("None",self)
        xlim_right=QLineEdit("None",self)

        ylim_top=QLineEdit("None",self)
        ylim_top.textChanged.connect(self.plot)
        ylim_bottom=QLineEdit("None",self)
        ylim_bottom.textChanged.connect(self.plot)

        xlim_left_label=QLabel("X min",self)
        xlim_right_label=QLabel("X max",self)

        ylim_top_label=QLabel("Y max",self)

        ylim_bottom_label=QLabel("Y min",self)
        l.addWidget(xlim_right_label,5,(100-3),1,1)
        l.addWidget(xlim_right,5,(100-2),1,2)
        l.addWidget(xlim_left_label,6,(100-3),1,1)
        l.addWidget(xlim_left,6,(100-2),1,2)

        l.addWidget(ylim_top_label,7,(100-3),1,1)
        l.addWidget(ylim_top,7,(100-2),1,2)
        l.addWidget(ylim_bottom_label,8,(100-3),1,1)
        l.addWidget(ylim_bottom,8,(100-2),1,2)
        self.compute_initial_figure()
        self.show()

    def compute_initial_figure(self):
            axes=self.figure.add_subplot(111)
            t = np.arange(0.0, 3.0, 0.01)
            s = np.sin(2*np.pi*t)
            axes.plot(t, s)
            self.canvas.draw()
            #axes.set_ylim(top=self.ylim_top.text(),bottom=self.ylim_bottom.text()) 
    def plot(self):
            plt.cla()
            axes=self.figure.add_subplot(111)
            t = np.arange(0.0, 3.0, 0.01)
            s = np.sin(2*np.pi*t)
            axes.plot(t, s)
            axes.set_ylim(top=self.ylim_top.text(),bottom=self.ylim_bottom.text()) 
            self.canvas.draw()

if __name__ == '__main__':
    sheets_idealcut=['pass2','pass3','pass4','pass5']

    app = QApplication(sys.argv)
    w = App()
    app.exec_()

I want it to change the Y axis limits in the figure based on user input in the Y max and Y min textboxes. Below is the output:

Problem is: the figure is not updating when I change the values in Y max and Y min textboxes. I used the QLineEdit.textChanged.connect function to connect the textbox to the figure update function. However it seems the code is not entering into the plot function at all. What am I doing wrong here ?

Please help. (1.I use grid layout so that I can adjust the widget size and positions as desired. 2. This is the reference code that I used to base my code on. This reference uses pyqt4.)

Answer 1

I would expect that the code throws an error, because you are trying to set the ylimits as strings.

The ylimits should be numerical values, so one would need to convert the texts from the input fields to numbers.

axes.set_ylim(top=float(self.ylim_top.text()),bottom=float(self.ylim_bottom.text()))

Apart from that it may not be a good idea to clear the axes and add a new subplot each time the values in the text inputs are changed. Instead you may use the same axes (call it self.axes ) to operate on.