MATLAB-like drawnow to easily update a figure
Python Matlab
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drawnow for matplotlib

The scientific community often runs iterative code, often in the form of simulation. It's often useful to see the results after each iteration. Accordingly, MATLAB® has a nice feature that allows you to update the figure, drawnow. This repo brings the same feature to Python's matplotlib, with some extras.


This is shown with imshow, but python-drawnow allows updates of any figure.


# complete implementation of script found in test/
from pylab import *
from drawnow import drawnow, figure
# if global namespace, import plt.figure before drawnow.figure

figure(figsize=(7, 7/2))
def draw_fig():
    subplot(1, 2, 1)

    subplot(1, 2, 2)

x = imread('mandrill.png').mean(axis=2)
k_values = around(logspace(0, 2, num=10))
for k in k_values:
    x_hat = approx(x, k)


If you want to wait for confirmation after update or the option to drop into a debugger, call drawnow(function_to_draw_figure, confirm=True).

If you only want to show the figure once, call drawnow(function_to_draw_figure, show_once=True)

drawnow does not work in IPython's QtConsole at least for me.

The full documentation is included in the doc strings.


Two options:

  1. Run pip install drawnow.
  2. Download this repository and run python install.

Changes to code

This does require small changes to your code. All it should really amount to is moving figure(); plot(...); show() inside a function; not much.