make decompress_file a context manager and create compression fixture

Author: reidy-p

pandas/tests/conftest.py

@@ -0,0 +1,12 @@
+import pytest
+import pandas
+import pandas.util._test_decorators as td
+
+
+@pytest.fixture(params = [None, 'gzip', 'bz2',
+                          pytest.param('xz', marks=td.skip_if_no_lzma)])
+def compression(request):
+    """
+    Fixture for trying common compression types in compression tests
+    """
+    return request.param

pandas/tests/frame/test_to_csv.py

@@ -920,12 +920,6 @@ def test_to_csv_path_is_none(self):
         recons = pd.read_csv(StringIO(csv_str), index_col=0)
         assert_frame_equal(self.frame, recons)
 
-    @pytest.mark.parametrize('compression', [
-        None,
-        'gzip',
-        'bz2',
-        pytest.param('xz', marks=td.skip_if_no_lzma),
-    ])
     def test_to_csv_compression(self, compression):
 
         df = DataFrame([[0.123456, 0.234567, 0.567567],
@@ -941,14 +935,13 @@ def test_to_csv_compression(self, compression):
             assert_frame_equal(df, rs)
 
             # explicitly make sure file is compressed
-            f = tm.decompress_file(filename, compression)
-            text = f.read().decode('utf8')
-            for col in df.columns:
-                assert col in text
-            f.close()
-
-            f = tm.decompress_file(filename, compression)
-            assert_frame_equal(df, read_csv(f, index_col=0))
+            with tm.decompress_file(filename, compression) as fh:
+                text = fh.read().decode('utf8')
+                for col in df.columns:
+                    assert col in text
+
+            with tm.decompress_file(filename, compression) as fh:
+                assert_frame_equal(df, read_csv(fh, index_col=0))
 
     def test_to_csv_compression_value_error(self):
         # GH7615

pandas/util/testing.py

@@ -162,6 +162,7 @@ def round_trip_localpath(writer, reader, path=None):
     return obj
 
 
+@contextmanager
 def decompress_file(path, compression):
     """
     Open a compressed file and return a file object
@@ -194,7 +195,7 @@ def decompress_file(path, compression):
         msg = 'Unrecognized compression type: {}'.format(compression)
         raise ValueError(msg)
 
-    return f
+    yield f
 
 
 def assert_almost_equal(left, right, check_exact=False,