mplwidget.py

# Imports
from PyQt6 import QtWidgets
#from matplotlib.figure import Figure
import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as Canvas
import matplotlib
from matplotlib.artist import Artist
# Ensure using PyQt5 backend
matplotlib.use('QT5Agg')

# Matplotlib canvas class to create figure

class MplCanvas(Canvas):
    def __init__(self):
        self.fig = plt.figure()  
        self.plt = plt
        self.ax = self.fig.add_subplot(111)

        Canvas.__init__(self, self.fig)
        #Canvas.setSizePolicy(self, QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        Canvas.updateGeometry(self)

# Matplotlib widget
class MplWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        QtWidgets.QWidget.__init__(self, parent)   # Inherit from QWidget
        self.canvas = MplCanvas()                  # Create canvas object
        self.vbl = QtWidgets.QVBoxLayout()         # Set box for plotting
        self.vbl.addWidget(self.canvas)
        self.setLayout(self.vbl)