Legend color race condition

[jimrybarski]

The colors of the symbols in my legend vary randomly each time I make a plot or save it to disk. It shifts between a set of three colors, one of which is completely correct, one of which has a single incorrect color, and one which is all wrong. Run the demo code below several times to see this. I have reproduced this on two separate machines, one of which is running the code in a Docker container.

I have noticed the Please do not ask for support with these customizations active. but since it lists nothing, I'm not sure what to make of that.

matplotlib version: 1.4.3
backend: Qt5Agg version 5.3.2

import matplotlib.pyplot as plt
import random

blue = [.365, .647, .855]
green = [.376, .741, .408]
purple = [.698, .463, .698]


def boxplot(data, title, x_label, y_label, legend_location="upper left"):
    fig = plt.figure(1, figsize=(9, 6))
    ax = fig.add_subplot(111)
    meanprops = dict(linestyle='-', linewidth=1.5, color=purple)
    boxprops = dict(linewidth=1.5, color=blue)
    whiskerprops = dict(linewidth=1.5, color=blue)
    capprops = dict(linewidth=1.5, color=blue)
    medianprops = dict(alpha=0.0)
    flierprops = dict(marker='+', color=green, markersize=12, mew=2)

    plt.plot([], c=purple, label='Mean', linewidth=1.5)
    plt.plot([], c=blue, label='1st Quartile', linewidth=1.5)
    plt.plot([], c=blue, label='3rd Quartile', linewidth=1.5, linestyle='--')
    plt.legend(loc=legend_location, numpoints=1)
    plt.plot([], c=green, label='Outlier', marker='+', markersize=12, mew=2, linestyle='')
    plt.legend(loc=legend_location, numpoints=1)

    values = [a for d in data.values() for a in d]
    max_value = max(values)
    bp = ax.boxplot([d for n, d in sorted(data.items())],
                    meanprops=meanprops,
                    capprops=capprops,
                    flierprops=flierprops,
                    medianprops=medianprops,
                    boxprops=boxprops,
                    whiskerprops=whiskerprops,
                    showmeans=True,
                    meanline=True,
                    labels=[i for i in range(49)])
    ax.set_ylim([0, max_value + 2])
    ax.set_axis_bgcolor('white')
    ax.set_xlabel(x_label)
    ax.set_ylabel(y_label)
    plt.suptitle(title)
    fig = plt.gcf()
    fig.set_size_inches(20, 10)
    plt.show()
    plt.close()

if __name__ == '__main__':
    data = {j: [random.randint(10, 100) for i in range(100)] for j in range(49)}
    boxplot(data, "Race Condition Plots", "X Axis", "Y Axis")

$ python3.4 /opt/bug.py --verbose-helpful 

non-network local connections being added to access control list
$HOME=/root
matplotlib data path /usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data

*****************************************************************
You have the following UNSUPPORTED LaTeX preamble customizations:

Please do not ask for support with these customizations active.
*****************************************************************

loaded rc file /usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/matplotlibrc
matplotlib version 1.4.3
verbose.level helpful
interactive is False
platform is linux
CACHEDIR=/root/.cache/matplotlib
font search path ['/usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/fonts/ttf', '/usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/fonts/afm', '/usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/fonts/pdfcorefonts']
generated new fontManager
backend Qt5Agg version 5.3.2
1.4.3
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libGL error: failed to open drm device: No such file or directory
libGL error: failed to load driver: i965
libGL error: unable to load driver: swrast_dri.so
libGL error: failed to load driver: swrast
findfont: Matching :family=sans-serif:style=normal:variant=normal:weight=normal:stretch=normal:size=medium to Bitstream Vera Sans ('/usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/fonts/ttf/Vera.ttf') with score of 0.000000
findfont: Matching :family=sans-serif:style=normal:variant=normal:weight=normal:stretch=normal:size=large to Bitstream Vera Sans ('/usr/local/lib/python3.4/dist-packages/matplotlib/mpl-data/fonts/ttf/Vera.ttf') with score of 0.000000

[Tillsten]

You are assigning a empty linestyl, is that wanted?

[jimrybarski]

@Tillsten yes, since I only wanted to show a single marker for the outlier symbol, the line made no sense there. However, even if I add the line back in the color problem remains.

[tacaswell]

As a side note, what is wrong with Axes.bxp / Axes.boxplot? Sorry. I can't read

[tacaswell]

This is already fixed on master and will be released with 1.5.0 (there are rcs currently tagged, so soon).

As a work-around, for now use color=... instead of c=....

You also only need to call legend once.

[tacaswell]

See #5197, #5199, #4162,

fixed by #4198