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MATLAB-like drawnow

Project description

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

def approx(x, k):
    """Approximate x with k singular values"""

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

    subplot(1, 2, 2)

x = imread('test-data/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). The full documentation is included in the doc strings. Use drawnow? or help(drawnow) to see these docs.


Try running the folloowing code in a Jupyter input cell/in the console/etc:


This will disable the Matplotlin inline mode and use the default plotting backend. For more detail, see the IPython plotting documentation.


Two options:

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

Option 2 assumes a working Python installation with pip. I suggest Anaconda's distribution: For other options, see

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.

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