Clearer error message for plt.axis()

dstansby · dstansby · commit 016ed8730479 · 2019-07-23T09:05:44.000+01:00
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1660,11 +1660,15 @@ def axis(self, *args, emit=True, **kwargs):
                         "3.2", message="Passing more than one positional "
                         "argument to axis() is deprecated and will raise a "
                         "TypeError %(removal)s.")
-                v = args[0]
+                limits = args[0]
                 try:
-                    xmin, xmax, ymin, ymax = v
+                    xmin, xmax, ymin, ymax = limits
                 except ValueError:
                     raise ValueError('args must contain [xmin xmax ymin ymax]')
+                except TypeError:
+                    raise TypeError('the first argument to axis() must be an '
+                                    'interable of the form '
+                                    '[xmin, xmax, ymin, ymax]')
             else:
                 xmin = kwargs.pop('xmin', None)
                 xmax = kwargs.pop('xmax', None)
