contourf: raise ValueError if fewer than 2 levels are specified

efiring · efiring · commit 58c47131226e · 2011-06-16T13:12:04.000-10:00
There was already a check for this condition, but it needed to be
shifted slightly to handle all such cases.
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -895,9 +895,9 @@ def _contour_level_args(self, z, args):
                 except:
                     raise TypeError(
                         "Last %s arg must give levels; see help(%s)" % (fn,fn))
-            if self.filled and len(lev) < 2:
-                raise ValueError("Filled contours require at least 2 levels.")
             self.levels = lev
+        if self.filled and len(self.levels) < 2:
+            raise ValueError("Filled contours require at least 2 levels.")
 
     def _process_levels(self):
         self._levels = list(self.levels)
