Really simple demo

import os

import numpy as np
from qtpy.QtCore import Qt, QTimer

import qwt
from qwt.tests import utils

FNAMES = ("test_simple.svg", "test_simple.pdf", "test_simple.png")


class SimplePlot(qwt.QwtPlot):
    NUM_POINTS = 100
    TEST_EXPORT = True

    def __init__(self):
        qwt.QwtPlot.__init__(self)
        self.setTitle("Really simple demo")
        self.insertLegend(qwt.QwtLegend(), qwt.QwtPlot.RightLegend)
        self.setAxisTitle(qwt.QwtPlot.xBottom, "X-axis")
        self.setAxisTitle(qwt.QwtPlot.yLeft, "Y-axis")
        self.enableAxis(self.xBottom)
        self.setCanvasBackground(Qt.white)

        qwt.QwtPlotGrid.make(self, color=Qt.lightGray, width=0, style=Qt.DotLine)

        # insert a few curves
        x = np.linspace(0.0, 10.0, self.NUM_POINTS)
        qwt.QwtPlotCurve.make(x, np.sin(x), "y = sin(x)", self, linecolor="red")
        qwt.QwtPlotCurve.make(x, np.cos(x), "y = cos(x)", self, linecolor="blue")

        # insert a horizontal marker at y = 0
        qwt.QwtPlotMarker.make(
            label="y = 0",
            align=Qt.AlignRight | Qt.AlignTop,
            linestyle=qwt.QwtPlotMarker.HLine,
            color="darkGreen",
            plot=self,
        )

        # insert a vertical marker at x = 2 pi
        qwt.QwtPlotMarker.make(
            xvalue=2 * np.pi,
            label="x = 2 pi",
            align=Qt.AlignRight | Qt.AlignTop,
            linestyle=qwt.QwtPlotMarker.VLine,
            color="darkGreen",
            plot=self,
        )

        if self.TEST_EXPORT and utils.TestEnvironment().unattended:
            QTimer.singleShot(0, self.export_to_different_formats)

    def export_to_different_formats(self):
        for fname in FNAMES:
            self.exportTo(fname)


def test_simple():
    """Simple plot example"""
    utils.test_widget(SimplePlot, size=(600, 400))
    for fname in FNAMES:
        if os.path.isfile(fname):
            os.remove(fname)


if __name__ == "__main__":
    test_simple()