Animation interval and frames in Matplotlib - Step-by-Step Execution

Concept Flow - Animation interval and frames

Start Animation Setup

↓

Define frames count

↓

Set interval time

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For each frame in frames

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Update plot with new data

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Pause for interval ms

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Repeat until last frame

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End

Animation runs by updating plot data frame by frame, pausing for the set interval between frames until all frames are shown.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation

fig, ax = plt.subplots()
line, = ax.plot([], [])

ani = FuncAnimation(fig, lambda i: line.set_data([0, i], [0, i]), frames=5, interval=500)
plt.show()

This code animates a line growing from (0,0) to (4,4) in 5 steps, updating every 500 milliseconds.

Execution Table

Frame	i (frame index)	Action	Line Data Set	Wait (ms)
1	0	Set line data to ([0,0], [0,0])	([0,0], [0,0])	500
2	1	Set line data to ([0,1], [0,1])	([0,1], [0,1])	500
3	2	Set line data to ([0,2], [0,2])	([0,2], [0,2])	500
4	3	Set line data to ([0,3], [0,3])	([0,3], [0,3])	500
5	4	Set line data to ([0,4], [0,4])	([0,4], [0,4])	500
6	-	All frames done, animation ends	-	-

💡 Animation stops after frame 5, no more frames to update.

Variable Tracker

Variable	Start	After Frame 1	After Frame 2	After Frame 3	After Frame 4	After Frame 5
i (frame index)	-	0	1	2	3	4
line data	([], [])	([0,0], [0,0])	([0,1], [0,1])	([0,2], [0,2])	([0,3], [0,3])	([0,4], [0,4])

Key Moments - 3 Insights

Why does the animation stop after frame 5?

Because the frames parameter is set to 5, so the animation runs from i=0 to i=4 (5 frames total). See execution_table rows 1-6.

What does the interval parameter control?

It controls the pause time in milliseconds between frames. Here it is 500 ms, so the animation updates every half second. See execution_table column 'Wait (ms)'.

What happens if frames is increased but interval stays the same?

The animation will have more frames and run longer, but the time between each frame update stays 500 ms, so total animation duration increases.

Visual Quiz - 3 Questions

Look at the execution_table, what is the line data set at frame 3?

A ([0,2], [0,2])

B ([0,3], [0,3])

C ([0,1], [0,1])

D ([0,4], [0,4])

💡 Hint

Check execution_table row 3 under 'Line Data Set'

At which frame does the animation stop updating?

A Frame 4

B Frame 6

C Frame 5

D Frame 3

💡 Hint

See execution_table exit_note and last frame row

If interval is changed from 500 to 1000 ms, what changes in the execution_table?

A Line Data Set changes

B Wait (ms) column changes to 1000 for each frame

C Frames column changes to 10

D Frame count decreases

💡 Hint

Interval controls wait time between frames, see 'Wait (ms)' column

Concept Snapshot

Animation in matplotlib updates plot data frame by frame.
Use 'frames' to set how many updates happen.
Use 'interval' to set pause time (ms) between frames.
Each frame calls an update function to change plot data.
Animation stops after last frame is shown.

Full Transcript

This visualization shows how matplotlib animation works with frames and interval. The animation runs from frame 0 to frame 4 (5 frames total). At each frame, the line data updates to new coordinates. After setting the data, the animation waits for 500 milliseconds before moving to the next frame. When all frames are done, the animation stops. The 'frames' parameter controls how many updates happen, and 'interval' controls the pause time between updates. Changing frames changes animation length; changing interval changes speed between frames.