fourier_slider

Example Python program fourier_slider.py

Modules

• import sys
• from PyQt5.QtWidgets import (QMainWindow, QApplication, QDockWidget, QWidget,
• from PyQt5.QtCore import Qt
• import numpy
• from numpy import sin, pi
• import matplotlib.pyplot
• import matplotlib.backends.backend_qt5agg

Classes

• class MainWindow (QMainWindow):

Methods

• def init (self):
• def set_signal (self, num):
• def plot (self):

Code

Example Python PyQt program :

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys

from PyQt5.QtWidgets import (QMainWindow, QApplication, QDockWidget, QWidget,
                         QGridLayout, QSlider)
from PyQt5.QtCore import Qt

import numpy
from numpy import sin, pi
import matplotlib.pyplot
import matplotlib.backends.backend_qt5agg

class MainWindow (QMainWindow):

  x = numpy.linspace (0, 3, 500)
  signal = numpy.zeros_like(x)
  square = numpy.sign(sin(2*pi*x))

  def __init__ (self):
    QMainWindow.__init__ (self)
    self.setWindowTitle('Fourier approximation of a square wave')
    self.figure  = matplotlib.pyplot.figure ()
    self.drawing = self.figure.add_subplot (111)
    self.canvas  = matplotlib.backends.backend_qt5agg.FigureCanvasQTAgg (self.figure)

    self.setCentralWidget (self.canvas)

    dock = QDockWidget ("Value")
    self.addDockWidget (Qt.RightDockWidgetArea, dock)

    sliders = QWidget ()
    sliders_grid = QGridLayout (sliders)

    # Add slider
    sld = QSlider (Qt.Vertical, sliders)
    sld.setMinimum(1)
    sld.setTickPosition(3)
    sld.setMaximum(100)
    sld.setTickInterval(10)
    sld.valueChanged[int].connect (self.set_signal)
    sld.valueChanged.connect (self.plot)
    sliders_grid.addWidget (sld, 0, 1)

    dock.setWidget (sliders)

    self.plot ()

  def set_signal (self, num):
    self.signal = numpy.zeros_like(self.x)
    for k in range(1, num):
        self.signal += (4/pi)*sin(2*(2*k - 1) *pi * self.x)/(2*k - 1)


  def plot (self):
    self.drawing.hold (False)
    self.drawing.plot (self.x, self.square,
                       self.x, self.signal, '--')
    self.drawing.set_ylim (-2, 2)
    self.canvas.draw ()

if __name__ == "__main__":
  app = QApplication (sys.argv)
  main = MainWindow ()
  main.show ()
  sys.exit (app.exec_ ())

Useful Links

• Articles: https://python-commandments.org/
• PyQt: https://pythonpyqt.com/
• Tutorial: https://pythonprogramminglanguage.com/