How to use BytesIO with matplotlib and pyqt5?

Question

I made a graph in matplotlib, and wanted to make it in to an image and use it in my pyqt5 application. Someone suggested I use BytesIO for this. This is my code so far:

Drawing my graph:

...
plt.axis('equal')
buff = io.BytesIO()
plt.savefig(buff, format="png")
print(buff)
return buff

This is then called in another script:

def minionRatioGraphSetup(self, recentMinionRatioAvg):
    image = minionRatioGraph(recentMinionRatioAvg)
    label = QtWidgets.QLabel()
    pixmap = QtGui.QPixmap(image)
    label.setPixmap(pixmap)
    label.setGeometry(QtCore.QRect(0,0,200,200))

It stops working at pixmap = QtGui.QPixmap(image) and I'm unsure why. Also: How could I place this in my MainWindow? because I doubt the code there will work lol

Answer 1

I'm sure there is a solution using a buffer. However, it seems rather complicated to get the byte format correct. So an alternative is to save the image to disk, and then load it from there.

import sys
from PyQt4 import QtGui
import matplotlib.pyplot as plt
import numpy as np

def minionRatioGraph():
    plt.plot([1,3,2])
    plt.savefig(__file__+".png", format="png")


class App(QtGui.QWidget):

    def __init__(self):
        super(App, self).__init__()
        self.setGeometry(300, 300, 250, 150)
        self.setLayout(QtGui.QVBoxLayout())
        label = QtGui.QLabel()
        label2 = QtGui.QLabel("Some other text label") 

        minionRatioGraph()

        qimg = QtGui.QImage(__file__+".png")  
        pixmap = QtGui.QPixmap(qimg)

        label.setPixmap(pixmap)
        self.layout().addWidget(label)
        self.layout().addWidget(label2)
        self.show()


if __name__ == '__main__':
    app = QtGui.QApplication([])
    ex = App()
    sys.exit(app.exec_())