diff --git a/pandas/core/computation/eval.py b/pandas/core/computation/eval.py
index 196f4b2679576..f44fa347cb053 100644
--- a/pandas/core/computation/eval.py
+++ b/pandas/core/computation/eval.py
@@ -3,6 +3,7 @@
 """Top level ``eval`` module.
 """
 
+import warnings
 import tokenize
 from pandas.io.formats.printing import pprint_thing
 from pandas.core.computation.scope import _ensure_scope
@@ -303,7 +304,8 @@ def eval(expr, parser='pandas', engine=None, truediv=True,
                                  "if there is no assignment")
 
         # assign if needed
-        if env.target is not None and parsed_expr.assigner is not None:
+        assigner = parsed_expr.assigner
+        if env.target is not None and assigner is not None:
             target_modified = True
 
             # if returning a copy, copy only on the first assignment
@@ -317,22 +319,25 @@ def eval(expr, parser='pandas', engine=None, truediv=True,
 
             # TypeError is most commonly raised (e.g. int, list), but you
             # get IndexError if you try to do this assignment on np.ndarray.
+            # we will ignore numpy warnings here; e.g. if trying
+            # to use a non-numeric indexer
             try:
-                target[parsed_expr.assigner] = ret
+                with warnings.catch_warnings(record=True):
+                    target[assigner] = ret
             except (TypeError, IndexError):
                 raise ValueError("Cannot assign expression output to target")
 
             if not resolvers:
-                resolvers = ({parsed_expr.assigner: ret},)
+                resolvers = ({assigner: ret},)
             else:
                 # existing resolver needs updated to handle
                 # case of mutating existing column in copy
                 for resolver in resolvers:
-                    if parsed_expr.assigner in resolver:
-                        resolver[parsed_expr.assigner] = ret
+                    if assigner in resolver:
+                        resolver[assigner] = ret
                         break
                 else:
-                    resolvers += ({parsed_expr.assigner: ret},)
+                    resolvers += ({assigner: ret},)
 
             ret = None
             first_expr = False
diff --git a/pandas/core/groupby.py b/pandas/core/groupby.py
index 8db75accc84e5..bf2b598d4ff9e 100644
--- a/pandas/core/groupby.py
+++ b/pandas/core/groupby.py
@@ -1913,7 +1913,10 @@ def size(self):
         """
         ids, _, ngroup = self.group_info
         ids = _ensure_platform_int(ids)
-        out = np.bincount(ids[ids != -1], minlength=ngroup or None)
+        if ngroup:
+            out = np.bincount(ids[ids != -1], minlength=ngroup)
+        else:
+            out = ids
         return Series(out,
                       index=self.result_index,
                       dtype='int64')
diff --git a/pandas/io/json/json.py b/pandas/io/json/json.py
index be39f4baba0fb..32bab09a0c4ac 100644
--- a/pandas/io/json/json.py
+++ b/pandas/io/json/json.py
@@ -764,7 +764,7 @@ def _parse_numpy(self):
         if orient == "columns":
             args = loads(json, dtype=None, numpy=True, labelled=True,
                          precise_float=self.precise_float)
-            if args:
+            if len(args):
                 args = (args[0].T, args[2], args[1])
             self.obj = DataFrame(*args)
         elif orient == "split":
diff --git a/pandas/io/sas/sas7bdat.py b/pandas/io/sas/sas7bdat.py
index 1d57093585ef2..26e39f0df8b29 100644
--- a/pandas/io/sas/sas7bdat.py
+++ b/pandas/io/sas/sas7bdat.py
@@ -596,6 +596,7 @@ def read(self, nrows=None):
             nrows = self.row_count
 
         if len(self.column_types) == 0:
+            self.close()
             raise EmptyDataError("No columns to parse from file")
 
         if self._current_row_in_file_index >= self.row_count: