Backport PR #9743: FIX: check if contour level in format dictionary, or return a default

dstansby · MeeseeksDev[bot] · commit cd5ef3498849 · 2017-11-12T14:57:47.000Z
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -322,7 +322,7 @@ def get_text(self, lev, fmt):
             return lev
         else:
             if isinstance(fmt, dict):
-                return fmt[lev]
+                return fmt.get(lev, '%1.3f')
             elif callable(fmt):
                 return fmt(lev)
             else:
diff --git a/lib/matplotlib/tests/test_contour.py b/lib/matplotlib/tests/test_contour.py
@@ -143,6 +143,25 @@ def test_contour_empty_levels():
     assert len(record) == 1
 
 
+def test_contour_badlevel_fmt():
+    # test funny edge case from
+    # https://github.com/matplotlib/matplotlib/issues/9742
+    # User supplied fmt for each level as a dictionary, but
+    # MPL changed the level to the minimum data value because
+    # no contours possible.
+    # This would error out pre
+    # https://github.com/matplotlib/matplotlib/pull/9743
+    x = np.arange(9)
+    z = np.zeros((9, 9))
+
+    fig, ax = plt.subplots()
+    fmt = {1.: '%1.2f'}
+    with pytest.warns(UserWarning) as record:
+        cs = ax.contour(x, x, z, levels=[1.])
+        ax.clabel(cs, fmt=fmt)
+    assert len(record) == 1
+
+
 def test_contour_uniform_z():
 
     x = np.arange(9)
