ENH: string format None and None and not NaN

Author: wesm

pandas/core/common.py

@@ -595,6 +595,8 @@ def _make_int_format(x):
         return _make_int_format(s)
     else:
         if na_rep is not None and lib.checknull(s):
+            if s is None:
+                return 'None'
             return na_rep
         else:
             # object dtype

scripts/roll_median_leak.py

@@ -15,11 +15,10 @@
 proc = psutil.Process(pid)
 
 lst = SparseList()
-lst.append([5] * 5)
+lst.append([5] * 10000)
 lst.append(np.repeat(np.nan, 1000000))
 
-sdf = SparseDataFrame({'A' : lst.to_array()})
-
 for _ in xrange(10000):
     print proc.get_memory_info()
+    sdf = SparseDataFrame({'A' : lst.to_array()})
     chunk = sdf[sdf['A'] == 5]