How do I plot in real-time in a while loop?

python

real-time-plotting

matplotlib

performance-tweaks

byAnton Shumikhin·Feb 13, 2025

To plot in real-time, utilize matplotlib's FuncAnimation:

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

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

def init():
    ax.set_xlim(0, 2*np.pi)
    ax.set_ylim(-1, 1)
    return line,

def update(frame):
    x, y = line.get_data()
    x = np.append(x, frame)
    y = np.append(y, np.sin(frame)) # We're not plotting a map. So be sineful
    line.set_data(x, y)
    return line,

ani = FuncAnimation(fig, update, frames=np.linspace(0, 2*np.pi, 128), init_func=init, blit=True) # This line here is the MVP
plt.show()

The advantage of this efficient snippet is that it plots a sine curve dynamically, only refreshing the line as required, rather than redrawing the entire figure.

The Need for Speed: Real-Time Plot Optimization

Unleashing the Power of `plt.pause()`

The secret sauce for speedy real-time plotting lies in matplotlib's plt.pause() function:

# Somewhere in your infinity gauntlet loop:
plt.pause(0.05) # Quick nap time before next iteration

It's our superhero that facilitates GUI event processing, thereby ensuring a pleasant real-time data interaction.

Battling the Redrawing Overhead with blit

Feeling the brunt of redrawing the whole figure? Fear not! Matplotlib's animation API with blit can be your mighty ally. The blit method redraws only specific sections of the plot, saving the day from heavy overheads. It's like cleaning just the corner where you spilled your coffee, instead of the whole kitchen floor.

Thread Safe Optimizations for GUI Integration

Into blending PyQt4/5 GUI applications with real-time plots? Going for threading or a thread-safe mechanism is your best bet. It's like having multiple chefs who know what they're doing in the kitchen simultaneously. They ensure your GUI doesn't quaver when stirred with data updates.

Under the Hood: Advanced Plot Performance Tweaks

Do right by your performance needs by measuring the average FPS. It's the speedometer you need to ensure your real-time plotting engine is purring like a kitten. Customizing GUI window, including zoom functionality, and caching the plot background are the cherries on top of your performance sundae.

In the Thick of Real-Time Plot Updates

Interactive Mode: Real-Time Plotting's Best Friend

For making your plot updates visible immediately as they arrive, turn on the matplotlib's interactive mode with plt.ion():

plt.ion() # Party mode on!

It's the secret handshake that enables live updates without halting the flow of your script.

Real Some Magic Points in a Loop

Penguin March with 'plt.scatter()'

When it comes to plotting individual points, let them march like Emperor Penguins! Use plt.scatter() in the loop for instant updates. Need to set boundaries? Use the strict plt.axis() just before your loop starts. Kick things off with plt.show(), and let your loop take care of the rest.

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