Raise exception if empty string given as column name (Issue pandas-dev#168) (pandas-dev#548)

* Raise exception if empty string given as column name (Issue pandas-dev#168)

* Remove range for python 3 compatibility

* updated_changelog

Author: srf94

CHANGES.md

@@ -1,6 +1,7 @@
 ## Changelog
 
 ### 1.66
+  * Bugfix: #168 Do not allow empty string as a column name
 
 ### 1.65 (2018-04-16)
   * Bugfix: #534 VersionStore: overwriting a symbol with different dtype (but same data format) does not

arctic/serialization/numpy_records.py

@@ -2,6 +2,7 @@
 import numpy as np
 
 from pandas import DataFrame, MultiIndex, Series, DatetimeIndex, Index
+from ..exceptions import ArcticException
 try:  # 0.21+ Compatibility
     from pandas._libs.tslib import Timestamp
     from pandas._libs.tslibs.timezones import get_timezone
@@ -110,6 +111,9 @@ def _to_records(self, df, string_max_len=None):
         index_names, ix_vals, metadata = self._index_to_records(df)
         columns, column_vals, multi_column = self._column_data(df)
 
+        if "" in columns:
+            raise ArcticException("Cannot use empty string as a column name.")
+
         if multi_column is not None:
             metadata['multi_column'] = multi_column
         metadata['columns'] = columns

tests/integration/store/test_version_store.py

@@ -14,7 +14,7 @@
 import numpy as np
 
 import arctic
-from arctic.exceptions import NoDataFoundException, DuplicateSnapshotException
+from arctic.exceptions import NoDataFoundException, DuplicateSnapshotException, ArcticException
 from arctic.date import DateRange
 from arctic.store import _version_store_utils
 
@@ -1393,3 +1393,11 @@ def test_prune_keeps_version(library):
     library._prune_previous_versions(symbol, keep_mins=0, keep_version=old_version)
 
     assert len(library.list_versions(symbol)) == 2
+
+
+def test_empty_string_column_name(library):
+    df = pd.DataFrame(data=[0, 1, 2], index=[0, 1, 2])
+    df.columns = ['']
+
+    with pytest.raises(ArcticException):
+        library.write('df', df)