PEP8:

jklymak · jklymak · commit a40d3b242cfb · 2018-03-19T13:33:21.000-07:00
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -798,19 +798,17 @@ def __init__(self, locator, tz=None, defaultfmt='%Y-%h-%d %H:%M:%S'):
         self._minutefmt = '%M'
         self._secondfmt = '%S'
 
-
     def __call__(self, x, pos=None):
         locator_unit_scale = float(self._locator._get_unit())
         dmin, dmax = self._locator.viewlim_to_dt()
         ticks = self._locator.tick_values(dmin, dmax)
-        if not pos is None:
+        if pos is not None:
             if not np.array_equal(ticks, self._oldticks):
 
                 fmt = self.defaultfmt
                 self._formatter = DateFormatter(fmt, self._tz)
                 tickdate = []
 
-
                 for nn, tick in enumerate(ticks):
                     tickdate += [num2date(tick)]
                 print(tickdate)
