How can you change how a matplotlib figure/axes is stretched when resizing the parent window in PyQt5?

Question

I have a program with an emedded figure that also shows a colorbar with custom tick labels. However, the automatic resizing of the figure cuts off part of the tick labels. This wouldn't be too bad if I could simply manually resize the window a bit so that everything is shown again. But, when you resize the window, the figure stretches in such a way that there is a large empty space created on the left side while the tick labels on the right can still not be completely seen unless you stretch the window unnecessarily wide. How can I change this behaviour? Below is an example. As you can see I already tried a few things but none of them worked.

import numpy as np
import sys
import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import \
    FigureCanvasQTAgg as FigureCanvas
import matplotlib.ticker as mticker


from PyQt5.QtWidgets import QApplication, QDialog, QGridLayout
from PyQt5.QtCore import QSize


class MathTextSciFormatter(mticker.Formatter):
    def __init__(self, fmt="%1.1e"):
        self.fmt = fmt

    def __call__(self, x, pos=None):
        s = self.fmt % x
        decimal_point = '.'
        positive_sign = '+'
        tup = s.split('e')
        significand = tup[0].rstrip(decimal_point)
        sign = tup[1][0].replace(positive_sign, '')
        exponent = tup[1][1:].lstrip('0')
        if exponent:
            exponent = '10^{%s%s}' % (sign, exponent)
        if significand and exponent:
            s = r'%s{\times}%s' % (significand, exponent)
        else:
            s = r'%s%s' % (significand, exponent)
        return "${}$ W/m${{}}^2$".format(s)


class Test(QDialog):
    def __init__(self):
        super().__init__()
        self.lay = QGridLayout(self)
        self.fig, self.ax = plt.subplots()
        # self.ax.set_anchor('SW')
        # self.ax.set_position([0, 0, 0, 0])
        # self.fig.tight_layout()
        # self.ax.margins(0, 0)
        self.canvas = FigureCanvas(self.fig)
        self.lay.addWidget(self.canvas)
        self.resize(QSize(380, 290))
        self.setMaximumHeight(290)
        self.image = np.reshape(np.random.randint(0, 1000, 10000), (100, 100))
        self.image_artist = self.ax.imshow(self.image)
        self.colorbar = self.fig.colorbar(self.image_artist)
        self.colorbar.ax.yaxis.set_major_formatter(
            MathTextSciFormatter()
        )


if __name__ == '__main__':
    app = QApplication(sys.argv)
    test = Test()
    test.show()
    sys.exit(app.exec_())

Thank you, if you like to formulate an answer, I'll accept it! However, now I have a new problem... https://stackoverflow.com/questions/60209169/what-is-the-proper-way-of-re-adding-axes-to-a-matplotlib-figure-while-maintainin — mapf, Feb 13 '20 at 13:40

score 0 · Accepted Answer · answered Feb 14 '20 at 09:14

As pointed out by ImportanceOfBeingErnest in a comment, making use of constrained_layout does the trick.

import numpy as np
import sys
import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import \
    FigureCanvasQTAgg as FigureCanvas
import matplotlib.ticker as mticker


from PyQt5.QtWidgets import QApplication, QDialog, QGridLayout
from PyQt5.QtCore import QSize


class MathTextSciFormatter(mticker.Formatter):
    def __init__(self, fmt="%1.1e"):
        self.fmt = fmt

    def __call__(self, x, pos=None):
        s = self.fmt % x
        decimal_point = '.'
        positive_sign = '+'
        tup = s.split('e')
        significand = tup[0].rstrip(decimal_point)
        sign = tup[1][0].replace(positive_sign, '')
        exponent = tup[1][1:].lstrip('0')
        if exponent:
            exponent = '10^{%s%s}' % (sign, exponent)
        if significand and exponent:
            s = r'%s{\times}%s' % (significand, exponent)
        else:
            s = r'%s%s' % (significand, exponent)
        return "${}$ W/m${{}}^2$".format(s)


class Test(QDialog):
    def __init__(self):
        super().__init__()
        self.lay = QGridLayout(self)
        self.fig, self.ax = plt.subplots(constrained_layout=True)
        # self.ax.set_anchor('SW')
        # self.ax.set_position([0, 0, 0, 0])
        # self.fig.tight_layout()
        # self.ax.margins(0, 0)
        self.canvas = FigureCanvas(self.fig)
        self.lay.addWidget(self.canvas)
        self.resize(QSize(380, 290))
        self.setMaximumHeight(290)
        self.image = np.reshape(np.random.randint(0, 1000, 10000), (100, 100))
        self.image_artist = self.ax.imshow(self.image)
        self.colorbar = self.fig.colorbar(self.image_artist)
        self.colorbar.ax.yaxis.set_major_formatter(
            MathTextSciFormatter()
        )


if __name__ == '__main__':
    app = QApplication(sys.argv)
    test = Test()
    test.show()
    sys.exit(app.exec_())

How can you change how a matplotlib figure/axes is stretched when resizing the parent window in PyQt5?

1 Answers1