Merge pull request #12927 from rth/fix-zip-unpacking

QuLogic · web-flow · commit 48f8cb93c67d · 2018-12-09T20:49:13.000-05:00
MAINT: Correctly handle empty lists in zip unpacking in mplot3d.art3d
diff --git a/lib/mpl_toolkits/mplot3d/art3d.py b/lib/mpl_toolkits/mplot3d/art3d.py
@@ -191,8 +191,12 @@ def path_to_3d_segment_with_codes(path, zs=0, zdir='z'):
     zs = np.broadcast_to(zs, len(path))
     pathsegs = path.iter_segments(simplify=False, curves=False)
     seg_codes = [((x, y, z), code) for ((x, y), code), z in zip(pathsegs, zs)]
-    seg, codes = zip(*seg_codes)
-    seg3d = [juggle_axes(x, y, z, zdir) for (x, y, z) in seg]
+    if seg_codes:
+        seg, codes = zip(*seg_codes)
+        seg3d = [juggle_axes(x, y, z, zdir) for (x, y, z) in seg]
+    else:
+        seg3d = []
+        codes = []
     return seg3d, list(codes)
 
 
@@ -204,7 +208,10 @@ def paths_to_3d_segments_with_codes(paths, zs=0, zdir='z'):
     zs = np.broadcast_to(zs, len(paths))
     segments_codes = [path_to_3d_segment_with_codes(path, pathz, zdir)
                       for path, pathz in zip(paths, zs)]
-    segments, codes = zip(*segments_codes)
+    if segments_codes:
+        segments, codes = zip(*segments_codes)
+    else:
+        segments, codes = [], []
     return list(segments), list(codes)
 
 
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -3,7 +3,7 @@
 from mpl_toolkits.mplot3d import Axes3D, axes3d, proj3d, art3d
 from matplotlib import cm
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
-from matplotlib.collections import LineCollection
+from matplotlib.collections import LineCollection, PolyCollection
 from matplotlib.patches import Circle
 import matplotlib.pyplot as plt
 import numpy as np
@@ -440,6 +440,13 @@ def test_poly3dcollection_closed():
     ax.add_collection3d(c2)
 
 
+def test_poly_collection_2d_to_3d_empty():
+    poly = PolyCollection([])
+    art3d.poly_collection_2d_to_3d(poly)
+    assert isinstance(poly, art3d.Poly3DCollection)
+    assert poly.get_paths() == []
+
+
 @image_comparison(baseline_images=['axes3d_labelpad'], extensions=['png'])
 def test_axes3d_labelpad():
     from matplotlib import rcParams
