How to instantly update the plot by getting values from a Scale widget?

[deanhystad]

I didn't understand what is the usage of set_array(x,y)

In the animation demo, and my subsequent reuse of that code, set_array(x, y) changes the data displayed in the plot.

This code change the values stored in the QuadMesh object self.mesh.

self.mesh.set_array(self.data[:-1, :-1, level].flatten())

When the plot is redrawn, it displays the new values.

self.figure.canvas.draw()

Your code does something different. Your code creates a new QuadMesh object.

ax.pcolormesh(x, y, layer, cmap=newcmp, edgecolor='lightgrey', linewidth=0.003)

This not only changes the data in the QuadMesh object (actually creates a new QuadMesh object), but it reconfigures the plot. The new plot might have different range. The labels might change.

The result is not much different. You see a plot of the new data. But your code is doing a lot more work then mine. This isn't really noticeable for your application, but it would be very noticeable if you had the plot changing several times a second. If I wanted to make a plot of real-time values, like an oscilloscope, I would not be pleased with the extra delay introduced by reconfiguring the entire plot each time I just added some now signal points.