matplotlib example draggable rectangle (snippet)

Python matplotlib example 'draggable rectangle'

Modules used in program:

• import matplotlib.pyplot as plt
• import numpy as np

python draggable rectangle

Python matplotlib example: draggable rectangle

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

import numpy as np
import matplotlib.pyplot as plt


class DraggableRectangle:
    def __init__(self, rect):
        self.rect = rect
        self.press = None

    def connect(self):
        'connect to all the events we need'
        self.cidpress = self.rect.figure.canvas.mpl_connect(
            'button_press_event', self.on_press)
        self.cidrelease = self.rect.figure.canvas.mpl_connect(
            'button_release_event', self.on_release)
        self.cidmotion = self.rect.figure.canvas.mpl_connect(
            'motion_notify_event', self.on_motion)

    def on_press(self, event):
        '''
        on button press we will see if the mouse is over us and store some data
        '''
        if event.inaxes != self.rect.axes:
            return

        contains, attrd = self.rect.contains(event)
        if not contains:
            return
        print('event contains', self.rect.xy)
        x0, y0 = self.rect.xy
        self.press = x0, y0, event.xdata, event.ydata

    def on_motion(self, event):
        'on motion we will move the rect if the mouse is over us'
        if self.press is None:
            return
        if event.inaxes != self.rect.axes:
            return
        x0, y0, xpress, ypress = self.press
        dx = event.xdata - xpress
        dy = event.ydata - ypress

        self.rect.set_x(x0 + dx)
        self.rect.set_y(y0 + dy)

        self.rect.figure.canvas.draw()

    def on_release(self, event):
        'on release we reset the press data'
        self.press = None
        self.rect.figure.canvas.draw()

    def disconnect(self):
        'disconnect all the stored connection ids'
        self.rect.figure.canvas.mpl_disconnect(self.cidpress)
        self.rect.figure.canvas.mpl_disconnect(self.cidrelease)
        self.rect.figure.canvas.mpl_disconnect(self.cidmotion)


if __name__ == '__main__':
    fig = plt.figure()
    ax = fig.add_subplot(111)
    rects = ax.bar(range(10), 20 * np.random.rand(10))
    drs = []
    for rect in rects:
        dr = DraggableRectangle(rect)
        dr.connect()
        drs.append(dr)

    plt.show()

Python links

• Learn Python: https://pythonbasics.org/
• Python Tutorial: https://pythonprogramminglanguage.com