Text alignment in a Matplotlib legend

Question

I am trying to right-align the entries in a matplotlib axes legend (by default they are left-aligned), but can’t seem to find any way of doing this. The setup I have is below:

(I have added data and labels to my_fig axes using the ax.plot() command)

ax = my_fig.get_axes()[0]
legend_font = FontProperties(size=10)
ax.legend(prop=legend_font, num_points=1, markerscale=0.5)

There is a list of legend keyword arguments in the docs for matplotlib Axes, but there doesn’t seem to be any straighforward way to set the alignment of the legend entries there. Anybody know of a backdoor way of doing this? Thanks.

EDIT:

To clarify what I am trying to achieve, right now my legend looks like:

Maneuver: 12-OCT-2011 12:00 UTC 

Bias: 14-OCT-2011 06:00 UTC

I want it to look like:

Maneuver: 12-OCT-2011 12:00 UTC 

    Bias: 14-OCT-2011 06:00 UTC

Asked By: jeremiahbuddha

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Source

Answer 1

The backdoor you’re looking for is the following:

# get the width of your widest label, since every label will need 
# to shift by this amount after we align to the right
shift = max([t.get_window_extent().width for t in legend.get_texts()])
for t in legend.get_texts():
    t.set_ha('right') # ha is alias for horizontalalignment
    t.set_position((shift,0))

Answered By: Paul Ivanov

Answer 2

I tried to get the example work, but I couldn’t.

At least since matplotlib version 1.1.1 (maybe earlier) we need a dedicated renderer instance.
Take care of your backend which defines the renderer. Depending on backend the output may look fine on screen but dismal as PDF.

# get the width of your widest label, since every label will need 
#to shift by this amount after we align to the right
renderer = figure.canvas.get_renderer()
shift = max([t.get_window_extent(renderer).width for t in legend.get_texts()])
for t in legend.get_texts():
    t.set_ha('right') # ha is alias for horizontalalignment
    t.set_position((shift,0))

Answered By: Peter

Answer 3

The answer of @Paul Ivanov took me into the right direction. But it needed a slight adaptation for me:

max_shift = max([t.get_window_extent().width for t in legend_obj.get_texts()])
for t in legend_obj.get_texts():
    t.set_ha('right')  # ha is alias for horizontalalignment
    temp_shift = max_shift - t.get_window_extent().width
    t.set_position((temp_shift, 0))

The change means that we set a different shift for each object based on its own width and the max width of the legend text.

For those that get the Cannot get window extent w/o renderer error, add a plt.pause(0.1) 🙂

Answered By: zwep

Text alignment in a Matplotlib legend

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