BUG: Respect usecols even with empty data

Closes pandas-devgh-12493.

Author: gfyoung

pandas/io/parsers.py

@@ -1255,10 +1255,19 @@ def read(self, nrows=None):
         except StopIteration:
             if self._first_chunk:
                 self._first_chunk = False
-                return _get_empty_meta(self.orig_names,
-                                       self.index_col,
-                                       self.index_names,
-                                       dtype=self.kwds.get('dtype'))
+
+                index, columns, col_dict = _get_empty_meta(
+                    self.orig_names, self.index_col,
+                    self.index_names, dtype=self.kwds.get('dtype'))
+
+                if self.usecols is not None:
+                    columns = self._filter_usecols(columns)
+
+                col_dict = dict(filter(lambda item: item[0] in columns,
+                                       col_dict.items()))
+
+                return index, columns, col_dict
+
             else:
                 raise
 

pandas/io/tests/test_parsers.py

@@ -3807,6 +3807,22 @@ def test_buffer_rd_bytes(self):
             except Exception as e:
                 pass
 
+    def test_read_empty_with_usecols(self):
+        # See gh-12493
+        names = ['Dummy', 'X', 'Dummy_2']
+        usecols = names[1:2] # ['X']
+
+        def check_usecols(stringIO, expected):
+            df = read_csv(stringIO, names=names, usecols=usecols)
+            tm.assert_frame_equal(df, expected)
+
+        expected = DataFrame(columns=usecols,
+                             index=[0], dtype=np.float64)
+        check_usecols(StringIO(',,'), expected)
+
+        expected = DataFrame(columns=usecols)
+        check_usecols(StringIO(''), expected)
+
 
 class TestCParserHighMemory(CParserTests, CompressionTests, tm.TestCase):
     engine = 'c'