Fix pyplot.axis(ax) when ax is in other figure.

lib/matplotlib/pyplot.py

@@ -875,7 +875,8 @@ def axes(*args, **kwargs):
       color for the axis, default white.
 
     - ``axes(h)`` where *h* is an axes instance makes *h* the current
-      axis.  An :class:`~matplotlib.axes.Axes` instance is returned.
+      axis and the parent of *h* the current figure.
+      An :class:`~matplotlib.axes.Axes` instance is returned.
 
     =========   ==============   ==============================================
     kwarg       Accepts          Description
@@ -909,7 +910,8 @@ def axes(*args, **kwargs):
     arg = args[0]
 
     if isinstance(arg, Axes):
-        a = gcf().sca(arg)
+        sca(arg)
+        a = arg
     else:
         rect = arg
         a = gcf().add_axes(rect, **kwargs)

lib/matplotlib/tests/test_axes.py

@@ -1477,6 +1477,17 @@ def _as_mpl_axes(self):
     plt.close()
 
 
+def test_pyplot_axes():
+    # test focusing of Axes in other Figure
+    fig1, ax1 = plt.subplots()
+    fig2, ax2 = plt.subplots()
+    assert ax1 is plt.axes(ax1)
+    assert ax1 is plt.gca()
+    assert fig1 is plt.gcf()
+    plt.close(fig1)
+    plt.close(fig2)
+
+
 @image_comparison(baseline_images=['log_scales'])
 def test_log_scales():
     fig = plt.figure()