OrderedDict legends no longer work 2.1

Bug report

Legend handles and labels retrieval break as of 2.1.1. Trying to call ax.get_legend_handles_labels() results in a comparison ValueError being thrown. git bisect led to 4f594f4 being the start of the issue.

Code for reproduction

%matplotlib inline
import collections
import matplotlib.pyplot as plt
import numpy as np

X = np.random.randn(10)
Y = np.random.randn(10)
labels = ['a'] * 5 + ['b'] * 5
colors = ['r'] * 5 + ['g'] * 5

fig, ax = plt.subplots()
for x, y, label, color in zip(X, Y, labels, colors):
    ax.scatter(x, y, label=label, c=color)

handles, labels = ax.get_legend_handles_labels()

Actual outcome

...in _in_handles(h, l)
   1342                 pass
   1343             try:
-> 1344                 if f_h.get_facecolor() != h.get_facecolor():
   1345                     continue
   1346             except AttributeError:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Expected outcome

Produce a scatter plot, as expected. This worked in 2.1.0.

Matplotlib version

Operating system: Ubuntu 16.04 and macOS 10.13
Matplotlib version: 2.1.1
Matplotlib backend (print(matplotlib.get_backend())): agg on both
Python version: 3.5.4
Jupyter version (if applicable): 4.4.0
Other libraries:

Sorry this broke for you. Can you make a non-pandas example and I’ll try and look at what went wrong.

oops, sorry, this is a dupe and already fixed in master, and will soon be released on 2.1.2... See #10064

@jklymak

Thanks @jklymak, it seems that my first issue is resolved by the current HEAD, but a new issue remains through using the collections.OrderedDict legend "gathering" method. Not sure if code changed internally to not support taking ordered dict values/keys items or if a cast to list or something was removed.

Curious if this is a bug or not, as the collections.OrderedDict way is (anecdotally) the go-to method for getting the handles/labels correctly grouped for customizing a legend.

Same exact code as my first issue, but the final step of:

...
ax.legend(legend.values(), legend.keys(), loc=6, bbox_to_anchor=(1, 0.5))

Which produces the following error output:

~/Developer/.../.../.../report_functions.py in princincipal_coordinates(samples, data, features, category)
     85                     by_label.keys(),
     86                     bbox_to_anchor=(1, 1.5),
---> 87                     loc=6)
     88 
     89     text = 'Samples were rarefied to {} retaining {} of {} samples'

~/Developer/mc3/envs/.../lib/python3.5/site-packages/matplotlib/axes/_axes.py in legend(self, *args, **kwargs)
    554         if len(extra_args):
    555             raise TypeError('legend only accepts two non-keyword arguments')
--> 556         self.legend_ = mlegend.Legend(self, handles, labels, **kwargs)
    557         self.legend_._remove_method = lambda h: setattr(self, 'legend_', None)
    558         return self.legend_

~/Developer/mc3/envs/.../lib/python3.5/site-packages/matplotlib/legend.py in __init__(self, parent, handles, labels, loc, numpoints, markerscale, markerfirst, scatterpoints, scatteryoffsets, prop, fontsize, borderpad, labelspacing, handlelength, handleheight, handletextpad, borderaxespad, columnspacing, ncol, mode, fancybox, shadow, title, framealpha, edgecolor, facecolor, bbox_to_anchor, bbox_transform, frameon, handler_map)
    590         del locals_view
    591         # trim handles and labels if illegal label...
--> 592         for label, handle in zip(labels[:], handles[:]):
    593                 if (isinstance(label, six.string_types) and
    594                         label.startswith('_')):

TypeError: 'odict_keys' object is not subscriptable

Looks like we need something like

diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
index 9ce249a13..79b3846e3 100644
--- a/lib/matplotlib/legend.py
+++ b/lib/matplotlib/legend.py
@@ -589,16 +589,18 @@ class Legend(Artist):
             setattr(self, name, value)
         del locals_view
         # trim handles and labels if illegal label...
-        for label, handle in zip(labels[:], handles[:]):
-                if (isinstance(label, six.string_types) and
-                        label.startswith('_')):
-                    warnings.warn('The handle {!r} has a label of {!r} which '
-                                  'cannot be automatically added to the '
-                                  'legend.'.format(handle, label))
-                    labels.remove(label)
-                    handles.remove(handle)
+        _cleaned_labels = []
+        _cleaned_handles = []
+        for label, handle in zip(labels, handles):
+            if isinstance(label, six.string_types) and label.startswith('_'):
+                warnings.warn('The handle {!r} has a label of {!r} which '
+                              'cannot be automatically added to the legend.'
+                              .format(handle, label))
+            else:
+                _cleaned_labels.append(label)
+                _cleaned_handles.append(handle)
+        labels, handles = _cleaned_labels, _cleaned_handles
 
-        handles = list(handles)
         if len(handles) < 2:
             ncol = 1
         self._ncol = ncol

@jakereps

@jakereps I can guess what you are doing, but can you make it explicit? legends is not defined yet in your code snippet.

Again, it'd be clearer w/o pandas... No doubt @anntzer is correct, that we need to get rid of the [:], but it'd be nice to have a complete example to test.

Oh true, sorry about that, I copied from further into the real codebase, but forgot I didn't include the legend variable creation in the example.

Here's the example sans pandas:

import collections
import matplotlib.pyplot as plt
import numpy as np

X = np.random.randn(10)
Y = np.random.randn(10)
labels = ['a'] * 5 + ['b'] * 5
colors = ['r'] * 5 + ['g'] * 5

fig, ax = plt.subplots()
for x, y, label, color in zip(X, Y, labels, colors):
    ax.scatter(x, y, label=label, c=color)

handles, labels = ax.get_legend_handles_labels()
legend = collections.OrderedDict(zip(labels, handles))
ax.legend(legend.values(), legend.keys(), loc=6, bbox_to_anchor=(1, .5))

@jakereps

Thanks @jakereps if you are able to compare my PR that'd be great, but it works w/ the test above....

Will do! Currently installing the PR (dropped back to 2.1.0 as a stopgap, so rebuilding the dev install).

@jklymak

Perfect! Looks good to me! Thanks @jklymak and @anntzer!

Fixed via. #10263

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OrderedDict legends no longer work 2.1 #10262

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OrderedDict legends no longer work 2.1 #10262

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jklymak commented on Jan 16, 2018

jklymak commented on Jan 16, 2018

jakereps commented on Jan 16, 2018

anntzer commented on Jan 16, 2018

jklymak commented on Jan 16, 2018

jakereps commented on Jan 16, 2018

jklymak commented on Jan 16, 2018

jakereps commented on Jan 16, 2018

jakereps commented on Jan 16, 2018

dstansby commented on Jan 18, 2018

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