Create a two line legend in a bokeh plot

Question

I'm trying to create a Bokeh chart with alot of individual lines on it, 14 to be exact (not my idea, was told to do it this way). Problem is that the requested formatting has the legend horizontal along the bottom of the chart and it's to long to fit so I need it to be two lines and I can't seem to find any indication on how to do this. Hoping someone has had to tackle this before.

Current code with a single line legend.

#graph data to chart
r0  = p1.line(data['Time'], data['Signal 1'], line_color="MediumBlue")
r1  = p1.line(data['Time'], data['Signal 2'], line_color="MidnightBlue")
r2  = p1.line(data['Time'], data['Signal 3'], line_color="red", y_range_name="Temp")
r3  = p1.line(data['Time'], data['Signal 4']*10, line_color="gray", y_range_name="Temp")
r4  = p1.line(data['Time'], data['Signal 5']*3.281, line_color="gold")
r5  = p1.line(data['Time'], data['Signal 6'], line_color="brown", y_range_name="Temp")
r6  = p1.line(data['Time'], data['Signal 7'], line_color="tomato", y_range_name="Temp")
r7  = p1.line(data['Time'], data['Signal 8'], line_color="blue", line_dash="4 4", y_range_name="Temp")
r8  = p1.line(data['Time'], data['Signal 9'], line_color="cyan", y_range_name="Temp")
r9  = p1.line(data['Time'], data['Signal 10']*57.3, line_color="plum", y_range_name="Temp")
r10 = p1.line(data['Time'], data['Signal 11']*1.94, line_color="green", y_range_name="Temp")

#create html file
output_file("Engine_Disp_Test.html", title="Engine Disp Test")

#Configure Legend
legend=Legend(items=[
                     ("Signal 1" , [r0]),
                 ("Signal 2" , [r1]),
                 ("Signal 3" , [r2]),
                 ("Signal 4" , [r3]),
                 ("Signal 5", [r4]),
                 ("Signal 6", [r5]),
                 ("Signal 7", [r6]),
                 ("Signal 8", [r7]),
                 ("Signal 9", [r8]),
                 ("Signal 10", [r9]),
                 ("Signal 11", [r10])
                 ], location=(70,-10), orientation="horizontal")

Answer 1

As of Bokeh 0.12.4 there is nothing that will automatically let you split legends into multiple row (or columns). But you can work around it by adding two legends. Note that I tweaked the positions and also added a min_border_bottom value since since the bottom legend seemed to be cut off otherwise.

from bokeh.io import output_file, show
from bokeh.models import Legend
from bokeh.plotting import figure

p = figure(min_border_bottom=130)

r1 = p.line(x=[0, 1], y=1, line_width=2, color="red")
r2 = p.line(x=[0, 1], y=2, line_width=2, color="blue")
r3 = p.line(x=[0, 1], y=3, line_width=2, color="green")
r4 = p.line(x=[0, 1], y=4, line_width=2, color="orange")

legend1 = Legend([items=[("r1" , [r1]), ("r2", [r2])],
                 location=(70,20), orientation="horizontal")

legend2 = Legend(items=[("r3" , [r3]), ("r4", [r4])],
                 location=(70,10), orientation="horizontal")

p.add_layout(legend1, 'below')
p.add_layout(legend2, 'below')

output_file("foo.html")

show(p)