Update formatters.py

Use the float formatter for NumPy's float64 type.

IPython/core/formatters.py

@@ -678,6 +678,8 b' class PlainTextFormatter(BaseFormatter):'
     def _type_printers_default(self):
         d = pretty._type_pprinters.copy()
         d[float] = lambda obj,p,cycle: p.text(self.float_format%obj)
+        if 'numpy' in sys.modules:
+            d[numpy.float64] = lambda obj,p,cycle: p.text(self.float_format%obj)
         return d
 
     @default('deferred_printers')