ENH: add ntrheads option to feather-format IO (#16476)

ENH: add nthreads option to feather-format IO

Author: jreback

doc/source/whatsnew/v0.21.0.txt

@@ -35,6 +35,7 @@ Other Enhancements
 - ``RangeIndex.append`` now returns a ``RangeIndex`` object when possible (:issue:`16212`)
 - :func:`to_pickle` has gained a protocol parameter (:issue:`16252`). By default, this parameter is set to `HIGHEST_PROTOCOL <https://docs.python.org/3/library/pickle.html#data-stream-format>`__
 - :func:`api.types.infer_dtype` now infers decimals. (:issue: `15690`)
+- :func:`read_feather` has gained the ``nthreads`` parameter for multi-threaded operations (:issue:`16359`)
 
 .. _whatsnew_0210.api_breaking:
 

pandas/io/feather_format.py

@@ -43,6 +43,7 @@ def to_feather(df, path):
     df : DataFrame
     path : string
         File path
+
     """
     path = _stringify_path(path)
     if not isinstance(df, DataFrame):
@@ -83,7 +84,7 @@ def to_feather(df, path):
     feather.write_dataframe(df, path)
 
 
-def read_feather(path):
+def read_feather(path, nthreads=1):
     """
     Load a feather-format object from the file path
 
@@ -93,6 +94,10 @@ def read_feather(path):
     ----------
     path : string
         File path
+    nthreads : int, default 1
+        Number of CPU threads to use when reading to pandas.DataFrame
+
+       .. versionadded 0.21.0
 
     Returns
     -------
@@ -102,4 +107,8 @@ def read_feather(path):
 
     feather = _try_import()
     path = _stringify_path(path)
-    return feather.read_dataframe(path)
+
+    if feather.__version__ < LooseVersion('0.4.0'):
+        return feather.read_dataframe(path)
+
+    return feather.read_dataframe(path, nthreads=nthreads)

pandas/tests/io/test_feather.py

@@ -27,11 +27,11 @@ def check_error_on_write(self, df, exc):
             with ensure_clean() as path:
                 to_feather(df, path)
 
-    def check_round_trip(self, df):
+    def check_round_trip(self, df, **kwargs):
 
         with ensure_clean() as path:
             to_feather(df, path)
-            result = read_feather(path)
+            result = read_feather(path, **kwargs)
             assert_frame_equal(result, df)
 
     def test_error(self):
@@ -98,6 +98,12 @@ def test_unsupported_other(self):
         df = pd.DataFrame({'a': pd.period_range('2013', freq='M', periods=3)})
         self.check_error_on_write(df, ValueError)
 
+    @pytest.mark.skipif(fv < '0.4.0', reason='new in 0.4.0')
+    def test_rw_nthreads(self):
+
+        df = pd.DataFrame({'A': np.arange(100000)})
+        self.check_round_trip(df, nthreads=2)
+
     def test_write_with_index(self):
 
         df = pd.DataFrame({'A': [1, 2, 3]})