BUG: Issue 9798 fixed

BUG: #9798 `index_col` shouldn't accept the value `True`

move the check to ``TextFileReader`` ``clean_options``

Author: lucas

doc/source/whatsnew/v0.16.1.txt

@@ -96,3 +96,5 @@ Bug Fixes
 
 - Fixed bug where ``DataFrame.plot()`` raised an error when both ``color`` and ``style`` keywords were passed and there was no color symbol in the style strings (:issue:`9671`)
 - Bug in ``read_csv`` and ``read_table`` when using ``skip_rows`` parameter if blank lines are present. (:issue:`9832`)
+
+- Bug in ``read_csv()`` interprets ``index_col=True`` as ``1`` (:issue:`9798`)

pandas/io/parsers.py

@@ -652,6 +652,8 @@ def _clean_options(self, options, engine):
         # really delete this one
         keep_default_na = result.pop('keep_default_na')
 
+        if index_col is True:
+            raise ValueError("The value of index_col couldn't be 'True'")
         if _is_index_col(index_col):
             if not isinstance(index_col, (list, tuple, np.ndarray)):
                 index_col = [index_col]

pandas/io/tests/test_parsers.py

@@ -520,6 +520,11 @@ def test_usecols_index_col_False(self):
         df = self.read_csv(StringIO(s_malformed), usecols=cols, index_col=False)
         tm.assert_frame_equal(expected, df)
 
+    def test_index_col_is_True(self):
+        # Issue 9798
+        self.assertRaises(ValueError, self.read_csv, StringIO(self.ts_data),
+                          index_col=True)
+
     def test_converter_index_col_bug(self):
         # 1835
         data = "A;B\n1;2\n3;4"