add scrollbar to preserve figure size in PyQt5 when plotting multiple figures

Question

I am trying to plot multiple graphs in a pyqt5 window widget. I was able to do that but the size of the figure would just be "compressed" if I add more graphs to the window. See the comparison by running below code and clicking Push for Window 1 vs Push for Window 2.

I wanted to add a scrollbar to the canvas, so that I can preserve the size of the graphs, just like putting multiple graphs in a word file and use the scrollbar to move up and down to review the graphs. How should I do that?

import sys
import pandas as pd
import numpy as np

from PyQt5.QtWidgets import (
    QApplication,
    QLabel,
    QMainWindow,
    QPushButton,
    QVBoxLayout,
    QWidget,
)

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
import matplotlib.pyplot as plt

class AnotherWindow1(QWidget):


    def __init__(self):
        super().__init__()
        self.figure = plt.figure(figsize=(45,15))    
        self.canvas = FigureCanvas(self.figure)  
        layout = QVBoxLayout()
        button1 = QPushButton("Plot")
        button1.clicked.connect(self.plot)
        button2 = QPushButton("Back")
        button2.clicked.connect(self.close_window)
        layout.addWidget(button1)
        layout.addWidget(button2)
        layout.addWidget(self.canvas)
        self.setLayout(layout)

    def close_window(self):
        self.close()

    def plot(self):
        self.figure.clear()
        ax1 =  self.figure.add_subplot(111) 
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax1)
        self.canvas.draw()

class AnotherWindow2(QWidget):


    def __init__(self):
        super().__init__()
        self.figure = plt.figure(figsize=(45,15))    
        self.canvas = FigureCanvas(self.figure)  
        self.canvas2 = FigureCanvas(self.figure) 
        self.canvas3 = FigureCanvas(self.figure)  
        layout = QVBoxLayout()
        button1 = QPushButton("Plot")
        button1.clicked.connect(self.plot)
        button2 = QPushButton("Back")
        button2.clicked.connect(self.close_window)
        layout.addWidget(button1)
        layout.addWidget(button2)
        layout.addWidget(self.canvas)
        layout.addWidget(self.canvas2)
        layout.addWidget(self.canvas3)
        self.setLayout(layout)

    def close_window(self):
        self.close()

    def plot(self):
        self.figure.clear()
        ax1 =  self.figure.add_subplot(111) 
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax1)
        self.canvas.draw()
        ax2 =  self.figure.add_subplot(111) 
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax2)
        self.canvas2.draw()
        ax2 =  self.figure.add_subplot(111) 
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax2)
        self.canvas3.draw()

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.window1 = AnotherWindow1()
        self.window2 = AnotherWindow2()

        l = QVBoxLayout()
        button1 = QPushButton("Push for Window 1")
        button1.clicked.connect(self.show_window1)
        l.addWidget(button1)

        button2 = QPushButton("Push for Window 2")
        button2.clicked.connect(self.show_window2)
        l.addWidget(button2)

        w = QWidget()
        w.setLayout(l)
        self.setCentralWidget(w)

    def show_window1(self):
        self.window1.show()

    def show_window2(self):
        self.window2.show()


app = QApplication(sys.argv)
w = MainWindow()
w.show()
app.exec()

eyllanesc · Accepted Answer · 2021-08-01 23:45:44Z

You have to use a QScrollArea that contains a QWidget as a container for the canvas

import sys
import pandas as pd
import numpy as np

from PyQt5.QtWidgets import (
    QApplication,
    QLabel,
    QMainWindow,
    QPushButton,
    QScrollArea,
    QVBoxLayout,
    QWidget,
)

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure


class AnotherWindow1(QWidget):
    def __init__(self):
        super().__init__()

        self.figure = Figure(figsize=(45, 15))
        self.canvas = FigureCanvas(self.figure)

        button1 = QPushButton("Plot")
        button1.clicked.connect(self.plot)
        button2 = QPushButton("Back")
        button2.clicked.connect(self.close_window)

        layout = QVBoxLayout(self)
        layout.addWidget(button1)
        layout.addWidget(button2)
        layout.addWidget(self.canvas)

    def close_window(self):
        self.close()

    def plot(self):
        self.figure.clear()
        ax1 = self.figure.add_subplot(111)
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax1)
        self.canvas.draw()


class AnotherWindow2(QWidget):
    def __init__(self):
        super().__init__()
        self.figure = Figure(figsize=(45, 15))

        self.canvas = FigureCanvas(self.figure)
        self.canvas.setMinimumSize(640, 480)
        self.canvas2 = FigureCanvas(self.figure)
        self.canvas2.setMinimumSize(640, 480)
        self.canvas3 = FigureCanvas(self.figure)
        self.canvas3.setMinimumSize(640, 480)

        canvas_scrollarea = QScrollArea(widgetResizable=True)
        canvas_container = QWidget()
        canvas_scrollarea.setWidget(canvas_container)
        canvas_layout = QVBoxLayout(canvas_container)
        canvas_layout.addWidget(self.canvas)
        canvas_layout.addWidget(self.canvas2)
        canvas_layout.addWidget(self.canvas3)

        button1 = QPushButton("Plot")
        button1.clicked.connect(self.plot)
        button2 = QPushButton("Back")
        button2.clicked.connect(self.close_window)

        layout = QVBoxLayout(self)

        layout.addWidget(button1)
        layout.addWidget(button2)
        layout.addWidget(canvas_scrollarea)

    def close_window(self):
        self.close()

    def plot(self):
        self.figure.clear()
        ax1 = self.figure.add_subplot(111)
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax1)
        self.canvas.draw()
        ax2 = self.figure.add_subplot(111)
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax2)
        self.canvas2.draw()
        ax2 = self.figure.add_subplot(111)
        data = pd.DataFrame(np.random.rand(5))
        data.plot(ax=ax2)
        self.canvas3.draw()


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.window1 = AnotherWindow1()
        self.window2 = AnotherWindow2()

        button1 = QPushButton("Push for Window 1")
        button1.clicked.connect(self.show_window1)

        button2 = QPushButton("Push for Window 2")
        button2.clicked.connect(self.show_window2)

        w = QWidget()
        l = QVBoxLayout(w)
        l.addWidget(button1)
        l.addWidget(button2)
        self.setCentralWidget(w)

    def show_window1(self):
        self.window1.show()

    def show_window2(self):
        self.window2.show()


app = QApplication(sys.argv)
w = MainWindow()
w.show()
app.exec()

Thank you. I think this is a very informative and effective answer.

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