zooming with NavigationToolbar does not work in matplotlib with pyqt

Question

i try to plot data using python 2.7, matplotlib, qt5 (version 5.7) and pyqt5. i took an example and adapted it to my needs. i see the NavigationToolbar gets added to the plot window, but the zooming does not work. i'm not sure what the second argument of NavigationToolbar object should be?

import sys
import matplotlib
matplotlib.use("Qt5Agg")
from numpy import arange, sin, pi
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
from PyQt5.QtWidgets import QWidget, QMainWindow, QApplication, QSizePolicy, QVBoxLayout, QPushButton
from PyQt5.QtCore import *
from PyQt5.QtGui import QCursor

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):
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.fig = fig
        self.axes = fig.add_subplot(111)
        # 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)


class ApplicationWindow(QWidget):
    def __init__(self):
        QWidget.__init__(self)
        self.setAttribute(Qt.WA_DeleteOnClose)
        self.main_widget = QWidget(self)
        self.l = QVBoxLayout(self)
        but = QPushButton("make_new", self)
        but.clicked.connect(self.again)
        self.l.addWidget(but)

    def again(self):
        sc = MyStaticMplCanvas(self, width=5, height=4, dpi=100)
        self.sc = sc

        win = MyMplCanvas()
        win.fig = self.sc.fig
        FigureCanvas.__init__(win, win.fig)
        self.win = win

        self.mpl_toolbar = NavigationToolbar(self.sc, self.win)
        win.show()

qApp = QApplication(sys.argv)
aw = ApplicationWindow()
aw.show()
sys.exit(qApp.exec_())

Answer 1

here is how i fixed it if someone is interested as well:

import sys
import matplotlib
matplotlib.use("Qt5Agg")
import numpy as np
from numpy import arange, sin, pi
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
from PyQt5.QtWidgets import QWidget, QMainWindow, QApplication, QSizePolicy, QVBoxLayout, QPushButton
from PyQt5.QtCore import *
from PyQt5.QtGui import QCursor

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):
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.fig = fig
        self.axes = fig.add_subplot(111)
        # 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)

class PlotDialog(QWidget):
    def __init__(self):
        QWidget.__init__(self)

        self.plot_layout = QVBoxLayout(self)
        self.plot_canvas = MyStaticMplCanvas(self, width=5, height=4, dpi=100)

        self.navi_toolbar = NavigationToolbar(self.plot_canvas, self)
        self.plot_layout.addWidget(self.plot_canvas)  # the matplotlib canvas
        self.plot_layout.addWidget(self.navi_toolbar)

if __name__ == "__main__":
    import sys
    app = QApplication(sys.argv)
    dialog = PlotDialog()
    dialog.show()
    sys.exit(app.exec_())