在PyQt5 GUI中嵌入matplotlib时发生内存泄漏

Question

I built a Matplotlib GUI with Qt Designer basically following this tutorial . I am using python 3.5.2 and pyqt 5.6.0 . The code you can see below is working. However when changing the plots the memory used by my system increases, at least according to Windows 10 Task Manager. To recreate this a little better one can increase the number of random values used in the plot commands. It seems like the self.canvas.close() command inside the rmmppl function is not enough to actually free the used memory.

How can I prevent the increasing memory usage?

edit: here is a Screenshot of the GUI

from PyQt5 import QtCore, QtGui, QtWidgets
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import (
FigureCanvasQTAgg as FigureCanvas,
NavigationToolbar2QT as NavigationToolbar)
import window
import numpy as np


class Plotter(QtWidgets.QMainWindow, window.Ui_MainWindow):
    def __init__(self):
        super(Plotter, self).__init__()
        self.setupUi(self)
        self.fig_dict = {}    
        self.mplfigs.itemClicked.connect(self.changefig)

    def addmpl(self, fig):
        self.canvas = FigureCanvas(fig)
        self.mplvl.addWidget(self.canvas)
        self.canvas.draw()
        self.toolbar = NavigationToolbar(self.canvas,self.mplwindow, coordinates = True)
        self.mplvl.addWidget(self.toolbar)

    def rmmppl(self):
        self.mplvl.removeWidget(self.canvas)
        self.canvas.close()
        self.mplvl.removeWidget(self.toolbar)
        self.toolbar.close()

    def addfig(self, name, fig):
        self.fig_dict[name]=fig
        self.mplfigs.addItem(name)

    def changefig(self,item):
        text = item.text()
        self.rmmppl()
        self.addmpl(self.fig_dict[text])



def main():
    import sys

    fig1 = Figure()
    ax1f1= fig1.add_subplot(111)
    ax1f1.plot(np.random.rand(5))

    fig2 = Figure()
    ax1f2 = fig2.add_subplot(121)
    ax1f2.plot(np.random.rand(5))
    ax1f2 = fig2.add_subplot(122)
    ax1f2.plot(np.random.rand(10))    

    app=QtWidgets.QApplication(sys.argv)
    main=Plotter()
    main.addmpl(fig1)
    main.addfig('Figure 1', fig1)
    main.addfig('Figure 2', fig2)
    main.show()

    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

The window.py which is the Basic GUI structure:

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(640, 432)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.horizontalLayout = QtWidgets.QHBoxLayout(self.centralwidget)
        self.horizontalLayout.setObjectName("horizontalLayout")
        self.mplwindow = QtWidgets.QWidget(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.mplwindow.sizePolicy().hasHeightForWidth())
        self.mplwindow.setSizePolicy(sizePolicy)
        self.mplwindow.setObjectName("mplwindow")
        self.mplvl = QtWidgets.QVBoxLayout(self.mplwindow)
        self.mplvl.setContentsMargins(0, 0, 0, 0)
        self.mplvl.setObjectName("mplvl")
        self.horizontalLayout.addWidget(self.mplwindow)
        self.mplfigs = QtWidgets.QListWidget(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Maximum, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.mplfigs.sizePolicy().hasHeightForWidth())
        self.mplfigs.setSizePolicy(sizePolicy)
        self.mplfigs.setMaximumSize(QtCore.QSize(200, 16777215))
        self.mplfigs.setMinimumSize(QtCore.QSize(200, 0))
        self.mplfigs.setObjectName("mplfigs")
        self.horizontalLayout.addWidget(self.mplfigs)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 640, 31))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))

Answer 1

I have executed your code on Linux and I have observed the same memory leak. Try with this:

Import the garbage collector with:

import gc

Then modify your rmmppl method:

def rmmppl(self):
    self.canvas.close()
    self.canvas.deleteLater()
    self.toolbar.close()
    self.toolbar.deleteLater()
    gc.collect()

Here is the documentation for deleteLater QObject Class Documentation