Connecting to Keypress Events

Introduction

In this lab, we will learn how to connect to keypress events in Matplotlib, which allows us to perform certain actions when a key is pressed. We will create a plot and set up a keypress event listener that will toggle the visibility of the x-label when the 'x' key is pressed.

VM Tips

After the VM startup is done, click the top left corner to switch to the Notebook tab to access Jupyter Notebook for practice.

Sometimes, you may need to wait a few seconds for Jupyter Notebook to finish loading. The validation of operations cannot be automated because of limitations in Jupyter Notebook.

If you face issues during learning, feel free to ask Labby. Provide feedback after the session, and we will promptly resolve the problem for you.

Import Libraries

We begin by importing the required libraries: matplotlib.pyplot and numpy.

import matplotlib.pyplot as plt
import numpy as np

Define the Keypress Event Function

Next, we define a function on_press that will be called when a key is pressed. This function takes an event parameter which contains information about the key that was pressed. In this example, we will toggle the visibility of the x-label when the 'x' key is pressed.

def on_press(event):
    print('press', event.key)
    sys.stdout.flush()
    if event.key == 'x':
        visible = xl.get_visible()
        xl.set_visible(not visible)
        fig.canvas.draw()

Create the Plot and Connect the Keypress Event Listener

We create a simple plot using np.random.rand() to generate random data. Then, we set up the keypress event listener using fig.canvas.mpl_connect() and passing in the name of the event we want to listen for ('key_press_event') and the function we want to call when the event occurs (on_press).

fig, ax = plt.subplots()

fig.canvas.mpl_connect('key_press_event', on_press)

ax.plot(np.random.rand(12), np.random.rand(12), 'go')
xl = ax.set_xlabel('easy come, easy go')
ax.set_title('Press a key')
plt.show()

Run the Code

Save the code to a file and run it in a Python environment. A plot will be displayed with the x-label "easy come, easy go". When the 'x' key is pressed, the x-label will toggle between visible and invisible.

Summary

In this lab, we learned how to connect to keypress events in Matplotlib. We created a plot and set up a keypress event listener that toggles the visibility of the x-label when the 'x' key is pressed. This is just one example of what can be done with keypress events in Matplotlib.