ENH: Added file keyword to setp to redirect output

lib/matplotlib/artist.py

@@ -1526,6 +1526,12 @@ def setp(obj, *args, **kwargs):
       >>> setp(line)
           ... long output listing omitted
 
+    You may specify an output file to `setp` if `sys.stdout` is not
+    acceptable for some reason::
+
+      >>> with fopen('output.log') as f:
+      >>>     setp(line, file=f)
+
     :func:`setp` operates on a single instance or a list of instances.
     If you are in query mode introspecting the possible values, only
     the first instance in the sequence is used.  When actually setting
@@ -1548,12 +1554,16 @@ def setp(obj, *args, **kwargs):
 
     insp = ArtistInspector(obj)
 
-    if len(kwargs) == 0 and len(args) == 0:
-        print('\n'.join(insp.pprint_setters()))
-        return
+    # file has to be popped before checking if kwargs is empty
+    printArgs = {}
+    if 'file' in kwargs:
+        printArgs['file'] = kwargs.pop('file')
 
-    if len(kwargs) == 0 and len(args) == 1:
-        print(insp.pprint_setters(prop=args[0]))
+    if not kwargs and len(args) < 2:
+        if args:
+            print(insp.pprint_setters(prop=args[0]), **printArgs)
+        else:
+            print('\n'.join(insp.pprint_setters()), **printArgs)
         return
 
     if not cbook.iterable(obj):

lib/matplotlib/tests/test_artist.py

@@ -208,6 +208,14 @@ def test_properties():
         assert len(w) == 0
 
 
+@cleanup
+def test_setp():
+    sio = io.StringIO()
+    lines = plt.plot(range(3))
+    plt.setp(lines, 'zorder', file=sio)
+    assert sio.getvalue() == '  zorder: any number '
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule(argv=['-s', '--with-doctest'], exit=False)