Interactive animation with widgets in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the widget module needed for interactive sliders.

Matplotlib

from matplotlib import pyplot as plt
from matplotlib import animation
from matplotlib.widgets import [1]

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

ASlider

BButton

CCheckButtons

DRadioButtons

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing Button instead of Slider because both are widgets.

Using RadioButtons which are for selection, not sliding.

The Slider widget from matplotlib.widgets is used to create interactive sliders for animations.

2fill in blank

medium

Complete the code to create a figure and axis for plotting.

Matplotlib

fig, ax = plt.[1]()

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

Aplot

Bshow

Cfigure

Dsubplots

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.figure() which returns only the figure, not axes.

Using plt.plot() which creates a plot but not figure and axes objects.

plt.subplots() creates a figure and a set of subplots (axes) for plotting.

3fill in blank

hard

Fix the error in the animation function to update the line data.

Matplotlib

def update(frame):
    y = [i * frame for i in range(10)]
    line.set_[1](y)
    return line,

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

Aupdate_data

Bset_data

Cset_ydata

Dset_xdata

Attempts:

3 left

💡 Hint

Common Mistakes

Using set_data which requires both x and y data.

Using set_xdata which updates x-values, not y-values.

The set_ydata method updates the y-values of the line for animation.

4fill in blank

hard

Fill both blanks to create a Slider widget and set its position on the figure.

Matplotlib

ax_slider = plt.axes([[1], 0.05, 0.65, 0.03])
slider = Slider(ax_slider, '[2]', 0, 10, valinit=5)

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

A0.1

B0.2

CFrequency

DAmplitude

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0.2 for position which shifts slider too far right.

Labeling slider as 'Amplitude' when controlling frequency.

The slider position starts at 0.1 on the x-axis and is labeled 'Frequency' for controlling frequency.

5fill in blank

hard

Fill all three blanks to update the animation frame using slider value and redraw the line.

Matplotlib

def update(val):
    freq = slider.val
    y = [[1] * freq for [2] in range(10)]
    line.set_[3](y)
    fig.canvas.draw_idle()

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

Ai

Bi * 2

Cset_ydata

Dset_data

Attempts:

3 left

💡 Hint

Common Mistakes

Using set_data which requires both x and y data.

Using i * 2 instead of i for the loop variable.

We multiply each i by freq to get y-values, use i as loop variable, and update y-data of the line.

Practice

1. What is the main purpose of using widgets like Slider in matplotlib interactive animations?

easy

A. To save the plot as an image file

B. To allow users to change plot parameters dynamically

C. To add titles and labels to the plot

D. To change the color scheme of the plot automatically

Solution

1. Step 1: Understand the role of widgets

   Widgets like Slider let users interact with the plot by changing values live.

2. Step 2: Identify the purpose in interactive animation

   The Slider changes parameters, triggering plot updates dynamically.

3. Final Answer:

   To allow users to change plot parameters dynamically -> Option B

4. Quick Check:

   Widgets enable dynamic parameter changes = A [OK]

Hint: Widgets let users control plot parameters live [OK]

Common Mistakes:

• Thinking widgets save images
• Confusing widgets with static labels
• Assuming widgets change colors automatically

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

easy

A. from matplotlib.widgets import Slider

B. import matplotlib.slider as Slider

C. from matplotlib import Slider

D. import Slider from matplotlib.widgets

Solution

1. Step 1: Recall matplotlib widget import syntax

   Widgets are imported from matplotlib.widgets module.

2. Step 2: Match correct Python import statement

   The correct syntax is: from matplotlib.widgets import Slider

3. Final Answer:

   from matplotlib.widgets import Slider -> Option A

4. Quick Check:

   Correct import syntax = B [OK]

Hint: Widgets come from matplotlib.widgets module [OK]

Common Mistakes:

• Using wrong import syntax
• Trying to import Slider directly from matplotlib
• Using JavaScript-style import

3. Given this code snippet, what will be printed when the slider value changes to 5?

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

fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.25)

slider_ax = plt.axes([0.25, 0.1, 0.65, 0.03])
slider = Slider(slider_ax, 'Value', 0, 10, valinit=0)

def update(val):
    print(f'Slider value is {val}')

slider.on_changed(update)
slider.set_val(5)

medium

A. Slider value is 0

B. No output printed

C. Slider value is 5

D. Error: update function not called

Solution

1. Step 1: Understand slider.set_val triggers update

   Calling slider.set_val(5) changes slider value and calls update with val=5.

2. Step 2: Check update function output

   Update prints 'Slider value is 5' when called with val=5.

3. Final Answer:

   Slider value is 5 -> Option C

4. Quick Check:

   set_val triggers update with new value = C [OK]

Hint: set_val calls update with new slider value [OK]

Common Mistakes:

• Assuming initial value prints
• Thinking update is not called automatically
• Confusing slider value with initial valinit

4. What is wrong with this code snippet for updating a plot with a slider?

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

fig, ax = plt.subplots()
line, = ax.plot([0, 1, 2], [0, 1, 4])
slider_ax = plt.axes([0.25, 0.1, 0.65, 0.03])
slider = Slider(slider_ax, 'Scale', 0.1, 2.0, valinit=1)

def update(val):
    line.set_ydata([y * val for y in [0, 1, 4]])

slider.on_changed(update)
plt.show()

medium

A. Missing import for Slider

B. Slider range is invalid

C. Syntax error in update function

D. The plot does not update visually after slider changes

Solution

1. Step 1: Check update function behavior

   Update changes y-data but does not redraw or refresh the plot.

2. Step 2: Identify missing redraw call

   Missing call to redraw canvas (e.g., fig.canvas.draw_idle()) causes no visual update.

3. Final Answer:

   The plot does not update visually after slider changes -> Option D

4. Quick Check:

   Missing redraw causes no visual update = D [OK]

Hint: Always redraw canvas after changing plot data [OK]

Common Mistakes:

• Forgetting fig.canvas.draw_idle() after data update
• Assuming set_ydata auto-refreshes plot
• Ignoring slider range correctness

5. You want to create an interactive plot where a Button resets a Slider to its initial value and updates the plot accordingly. Which of the following code snippets correctly implements this behavior?

hard

A. def reset(event):
slider.set_val(slider.valinit)

button.on_clicked(reset)

B. def reset(event):
slider.reset(event)

button.on_clicked(reset)

C. def reset(event):
slider.val = slider.valinit

button.on_clicked(reset)

D. def reset(event):
slider.valinit = slider.val

button.on_clicked(reset)

Solution

1. Step 1: Understand slider reset methods

   Slider does not have a reset(event) method; use slider.set_val(slider.valinit) explicitly sets value and triggers update.

2. Step 2: Check which code resets slider and triggers update

   Using slider.set_val(slider.valinit) sets slider to initial value and calls update function.

3. Final Answer:

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

4. Quick Check:

   Use set_val(valinit) to reset and update = A [OK]

Hint: Use slider.set_val(slider.valinit) to reset and update plot [OK]

Common Mistakes:

• Passing event to slider.reset()
• Setting slider.val directly without update
• Changing valinit instead of current value