Support writing CSV to GCS

Author: bnaul

pandas/io/formats/csvs.py

@@ -22,10 +22,9 @@
     ABCMultiIndex, ABCPeriodIndex, ABCDatetimeIndex, ABCIndexClass)
 
 from pandas.io.common import (
-    _expand_user,
     _get_handle,
     _infer_compression,
-    _stringify_path,
+    get_filepath_or_buffer,
     UnicodeWriter,
 )
 
@@ -45,7 +44,9 @@ def __init__(self, obj, path_or_buf=None, sep=",", na_rep='',
         if path_or_buf is None:
             path_or_buf = StringIO()
 
-        self.path_or_buf = _expand_user(_stringify_path(path_or_buf))
+        self.path_or_buf, _, _, _ = get_filepath_or_buffer(
+            path_or_buf, encoding=encoding, compression=compression, mode=mode
+        )
         self.sep = sep
         self.na_rep = na_rep
         self.float_format = float_format

pandas/tests/io/test_gcs.py

@@ -26,6 +26,21 @@ def test_read_csv_gcs(mock):
     assert_frame_equal(df1, df2)
 
 
+@td.skip_if_no('gcsfs')
+def test_to_csv_gcs(mock):
+    df1 = DataFrame({'int': [1, 3], 'float': [2.0, np.nan], 'str': ['t', 's'],
+                     'dt': date_range('2018-06-18', periods=2)})
+    with mock.patch('gcsfs.GCSFileSystem') as MockFileSystem:
+        s = StringIO()
+        instance = MockFileSystem.return_value
+        instance.open.return_value = s
+
+        df1.to_csv('gs://test/test.csv', index=True)
+        df2 = read_csv(StringIO(s.getvalue()), parse_dates=['dt'], index_col=0)
+
+    assert_frame_equal(df1, df2)
+
+
 @td.skip_if_no('gcsfs')
 def test_gcs_get_filepath_or_buffer(mock):
     df1 = DataFrame({'int': [1, 3], 'float': [2.0, np.nan], 'str': ['t', 's'],