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Realtime Data Plotting in Python

May 8th, 2013 May 8th, 2013

Realtime Data Plotting in Python

WARNING: this project is largely outdated, and some of the modules are no longer supported by modern distributions of Python.For a more modern, cleaner, and more complete GUI-based viewer of realtime audio data (and the FFT frequency data), check out my Python Real-time Audio Frequency Monitor project. I love using python for handing data. Displaying it isn't always as easy. Python fast to write, and numpy, scipy, and matplotlib are an incredible combination. I love matplotlib for displaying data and use it all the time, but when it comes to realtime data visualization, matplotlib (admittedly) falls behind. Imagine trying to plot sound waves in real time. Matplotlib simply can't handle it. I've recently been making progress toward this end with PyQwt with the Python X,Y distribution. It is a cross-platform solution which should perform identically on Windows, Linux, and MacOS. Here's an example of what it looks like plotting some dummy data (a sine wave) being transformed with numpy.roll().

How did I do it? Easy. First, I made the GUI with QtDesigner (which comes with Python x,y). I saved the GUI as a .ui file. I then used the pyuic4 command to generate a python script from the .ui file. In reality, I use a little helper script I wrote designed to build .py files from .ui files and start a little "ui.py" file which imports all of the ui classes. It's overkill for this, but I'll put it in the ZIP anyway. Here's what the GUI looks like in QtDesigner:

After that, I tie everything together in a little script which updates the plot in real time. It takes inputs from button click events and tells a clock (QTimer) how often to update/replot the data. Replotting it involves just rolling it with numpy.roll(). Check it out: