Widget-based interactions (sliders, buttons) in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the slider widget from matplotlib.

Matplotlib

from matplotlib.widgets import [1]

Drag options to blanks, or click blank then click option'

AButton

BSlider

CRadioButtons

DCheckButtons

Attempts:

3 left

💡 Hint

Common Mistakes

Importing Button instead of Slider

Using RadioButtons or CheckButtons which are different widgets

The Slider widget allows interactive sliding control in matplotlib plots.

2fill in blank

medium

Complete the code to create a slider with label 'Amplitude' and range from 0 to 10.

Matplotlib

slider = Slider(ax=[1], label='Amplitude', valmin=0, valmax=10, valinit=5)

Drag options to blanks, or click blank then click option'

Aplt.axes([0.25, 0.1, 0.65, 0.03])

Bplt.plot()

Cplt.figure()

Dplt.subplot()

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.figure() which creates a whole figure, not an axes

Using plt.plot() which creates a plot line, not an axes

Using plt.subplot() which is for subplots, not slider axes

The slider needs an axes object to be placed on. plt.axes with position list defines this area.

3fill in blank

hard

Fix the error in the slider update function to correctly update the plot line's y-data.

Matplotlib

def update(val):
    amp = slider.val
    line.set_ydata([1])
    fig.canvas.draw_idle()

Drag options to blanks, or click blank then click option'

Aamp + np.sin(x)

Bnp.sin(x)

Camp / np.sin(x)

Damp * np.sin(x)

Attempts:

3 left

💡 Hint

Common Mistakes

Not multiplying by amp, so the slider has no effect

Adding or dividing by amp which changes the wave incorrectly

The y-data should be the sine wave multiplied by the amplitude slider value.

4fill in blank

hard

Fill both blanks to create a button that resets the slider to its initial value when clicked.

Matplotlib

button = Button(ax=[1], label='Reset')

def reset(event):
    slider.[2]()

Drag options to blanks, or click blank then click option'

Aplt.axes([0.8, 0.025, 0.1, 0.04])

Bplt.axes([0.1, 0.025, 0.1, 0.04])

Creset

Dreset_val()

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong axes position for the button

Calling a non-existent method like reset_val()

The button needs an axes to be placed on, and calling slider.reset() resets the slider to its initial value.

5fill in blank

hard

Fill both blanks to connect the slider and button widgets to update and reset the plot interactively.

Matplotlib

slider.on_changed([1])
button.on_clicked([2])
plt.show()  # Display the interactive plot

Drag options to blanks, or click blank then click option'

Aupdate

Breset

Cupdate()

Dreset()

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses when passing functions as callbacks

Mixing up update and reset functions

The slider calls the update function when changed, the button calls reset when clicked, and plt.show() displays the plot.

Practice

1. What is the main purpose of using sliders in matplotlib widget-based interactions?

easy

A. To save the plot as an image file

B. To trigger a one-time action when clicked

C. To display static text on the plot

D. To allow continuous adjustment of plot parameters interactively

Solution

1. Step 1: Understand slider functionality

   Sliders let users change values smoothly and continuously, affecting the plot dynamically.

2. Step 2: Compare with other widgets

   Buttons trigger actions on click, not continuous changes; text display and saving are unrelated.

3. Final Answer:

   To allow continuous adjustment of plot parameters interactively -> Option D

4. Quick Check:

   Sliders = continuous value change [OK]

Hint: Sliders adjust values smoothly; buttons act on clicks [OK]

Common Mistakes:

• Confusing sliders with buttons
• Thinking sliders trigger one-time actions
• Assuming sliders display text

2. Which of the following is the correct way to import the slider widget from matplotlib.widgets?

easy

A. from matplotlib import Slider

B. import Slider from matplotlib.widgets

C. from matplotlib.widgets import Slider

D. import matplotlib.widgets.Slider

Solution

1. Step 1: Recall Python import syntax

   The correct syntax to import a class from a module is: from module import ClassName.

2. Step 2: Match with options

   from matplotlib.widgets import Slider matches this syntax exactly for Slider from matplotlib.widgets.

3. Final Answer:

   from matplotlib.widgets import Slider -> Option C

4. Quick Check:

   Correct import syntax = from matplotlib.widgets import Slider [OK]

Hint: Use 'from module import Class' syntax for widgets [OK]

Common Mistakes:

• Using 'import Class from module' which is invalid
• Trying to import directly from matplotlib
• Using dot notation in import statement

3. What will be the output of the following code snippet?

import matplotlib.pyplot as plt
from matplotlib.widgets import Slider

fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.25)
ax_slider = plt.axes([0.25, 0.1, 0.65, 0.03])
slider = Slider(ax_slider, 'Val', 0, 10, valinit=5)
print(slider.val)

medium

A. 5

B. 10

C. 0

D. Error: Slider object has no attribute 'val'

Solution

1. Step 1: Understand Slider initialization

   The slider is created with valinit=5, which sets its initial value to 5.

2. Step 2: Check slider value attribute

   The current slider value is accessed by slider.val, which returns the initial value before any interaction.

3. Final Answer:

   5 -> Option A

4. Quick Check:

   Slider initial value = 5 [OK]

Hint: Slider.val shows current value, starts at valinit [OK]

Common Mistakes:

• Assuming slider.val is zero by default
• Expecting error accessing slider.val
• Confusing slider.val with slider.valmin or valmax

4. Identify the error in this code snippet that tries to create a button widget:

import matplotlib.pyplot as plt
from matplotlib.widgets import Button

fig, ax = plt.subplots()
button_ax = plt.axes([0.7, 0.05, 0.1, 0.075])
button = Button(button_ax, 'Click Me')
button.on_clicked = lambda event: print('Button clicked!')
plt.show()

medium

A. The event handler should be connected using on_clicked() method, not by assignment

B. The on_clicked method should be called, not assigned

C. The button label must be a number, not a string

D. plt.axes() cannot be used to create button axes

Solution

1. Step 1: Understand button event connection

   The correct way to connect a function to button clicks is using button.on_clicked(function), not by assigning to button.on_clicked.

2. Step 2: Identify the error in code

   The code incorrectly assigns a lambda to button.on_clicked instead of calling button.on_clicked(lambda).

3. Final Answer:

   The event handler should be connected using on_clicked() method, not by assignment -> Option A

4. Quick Check:

   Use on_clicked(func), not on_clicked = func [OK]

Hint: Connect events with on_clicked(func), not by assignment [OK]

Common Mistakes:

• Assigning function to on_clicked instead of calling it
• Using wrong axes for button
• Misunderstanding button label type

5. You want to create an interactive plot where a slider controls the frequency of a sine wave and a button resets the slider to its initial value. Which of the following code snippets correctly implements the button reset functionality?

hard

A. def reset(event):
slider.val = slider.valinit
button.on_clicked(reset)

B. def reset(event):
slider.set_val(slider.valinit)
button.on_clicked(reset)

C. def reset():
slider.set_val(slider.valinit)
button.on_clicked(reset)

D. def reset(event):
slider.valinit = 0
button.on_clicked(reset)

Solution

1. Step 1: Understand slider reset method

   The slider widget provides set_val(value) method to update its value programmatically and trigger updates.

2. Step 2: Check event handler signature and usage

   The reset function must accept an event argument and call slider.set_val(slider.valinit) to reset to initial value. def reset(event): slider.set_val(slider.valinit) button.on_clicked(reset) matches this.

3. Final Answer:

   def reset(event): slider.set_val(slider.valinit) button.on_clicked(reset) -> Option B

4. Quick Check:

   Use set_val(valinit) in event handler to reset slider [OK]

Hint: Use slider.set_val(valinit) inside button callback [OK]

Common Mistakes:

• Assigning slider.val directly without set_val()
• Missing event parameter in callback
• Changing valinit instead of resetting slider value