How to insert scale bar in a map in matplotlib

There is a an already existing class for scalebars in matplotlib called AnchoredSizeBar. In the below example AnchoredSizeBar is used to add a scalebar to an image (or map over a 100x100 meter area of randomness).

import numpy as npimport matplotlib.pyplot as pltfrom mpl_toolkits.axes_grid1.anchored_artists import AnchoredSizeBarimport matplotlib.font_manager as fmfontprops = fm.FontProperties(size=18)fig, ax = plt.subplots()ax.imshow(np.random.random((10,10)),extent=[0,100,0,100]) 

Extent defines the images max and min of the horizontal and vertical values.

scalebar = AnchoredSizeBar(ax.transData,                           20, '20 m', 'lower center',                            pad=0.1,                           color='white',                           frameon=False,                           size_vertical=1,                           fontproperties=fontprops)ax.add_artist(scalebar)

The four first arguments to AnchoredSizeBar are the transformation object of the coordinate system, scalebar length, label and location. Further optional arguments change the layout. These are explained in the documentation.

ax.set_yticks([])ax.set_xticks([])

This gives

I would try the matplotlib-scalebar package. (For something like your example c.)

Assuming you are plotting a map image with imshow or similar, and you know the pixel width/cell-size (the real-world equivalent size of one pixel on the map image), you can automatically create the scale bar:

This example is straight off the PyPi matplotlib-scalebar package page but here it is for completeness:

import matplotlib.pyplot as pltimport matplotlib.cbook as cbookfrom matplotlib_scalebar.scalebar import ScaleBarplt.figure()image = plt.imread(cbook.get_sample_data('grace_hopper.png'))plt.imshow(image)scalebar = ScaleBar(0.2) # 1 pixel = 0.2 meterplt.gca().add_artist(scalebar)plt.show()