From 9bf4238ade9599e489f49eaca81e9689859fc05c Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Sun, 22 Jan 2017 22:52:51 -0800
Subject: [PATCH] Cleanup: use `is not` instead of `not ... is`, etc.

---
 lib/matplotlib/axes/_axes.py     | 10 +++++-----
 lib/matplotlib/cbook/__init__.py |  7 ++-----
 lib/matplotlib/mlab.py           |  2 +-
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index adc3d2d9b7e8..365194575349 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -4002,16 +4002,16 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
         else:
             colors = None  # use cmap, norm after collection is created
 
-        # Anything in maskargs will be unchanged unless it is the same length
-        # as x:
-        maskargs = x, y, s, c, colors, edgecolors, linewidths
+        # `delete_masked_points` only modifies arguments of the same length as
+        # `x`.
         x, y, s, c, colors, edgecolors, linewidths =\
-            cbook.delete_masked_points(*maskargs)
+            cbook.delete_masked_points(
+                x, y, s, c, colors, edgecolors, linewidths)
 
         scales = s   # Renamed for readability below.
 
         # to be API compatible
-        if marker is None and not (verts is None):
+        if marker is None and verts is not None:
             marker = (verts, 0)
             verts = None
 
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
index 2b438423e1e1..08e7f098d583 100644
--- a/lib/matplotlib/cbook/__init__.py
+++ b/lib/matplotlib/cbook/__init__.py
@@ -1497,15 +1497,12 @@ def __iter__(self):
         The iterator is invalid if interleaved with calls to join().
         """
         self.clean()
-
-        class Token:
-            pass
-        token = Token()
+        token = object()
 
         # Mark each group as we come across if by appending a token,
         # and don't yield it twice
         for group in six.itervalues(self._mapping):
-            if not group[-1] is token:
+            if group[-1] is not token:
                 yield [x() for x in group]
                 group.append(token)
 
diff --git a/lib/matplotlib/mlab.py b/lib/matplotlib/mlab.py
index d5dd437f212d..ee456b7fc56b 100644
--- a/lib/matplotlib/mlab.py
+++ b/lib/matplotlib/mlab.py
@@ -3348,7 +3348,7 @@ def griddata(x, y, z, xi, yi, interp='nn'):
 
     # Remove masked points.
     mask = np.ma.getmask(z)
-    if not (mask is np.ma.nomask):
+    if mask is not np.ma.nomask:
         x = x.compress(~mask)
         y = y.compress(~mask)
         z = z.compressed()