Fix handling of EOF in 'c' csv parser

doc/source/whatsnew/v0.17.0.txt

@@ -649,6 +649,7 @@ Bug Fixes
 - Bug in ``Categorical`` may not representing properly when category contains ``tz`` or ``Period`` (:issue:`10713`)
 - Bug in ``Categorical.__iter__`` may not returning correct ``datetime`` and ``Period`` (:issue:`10713`)
 
+- Bug in ``read_csv`` with ``engine='c'``: EOF preceded by a comment, blank line, etc. was not handled correctly (:issue:`10728`, :issue:`10548`)
 
 - Reading "famafrench" data via ``DataReader`` results in HTTP 404 error because of the website url is changed (:issue:`10591`).
 - Bug in ``read_msgpack`` where DataFrame to decode has duplicate column names (:issue:`9618`)

pandas/io/tests/test_parsers.py

@@ -2433,6 +2433,75 @@ def test_empty_with_nrows_chunksize(self):
         result = pd.DataFrame(result[2], columns=result[1], index=result[0])
         tm.assert_frame_equal(pd.DataFrame.from_records(result), expected)
 
+    def test_eof_states(self):
+        # GH 10728 and 10548
+
+        ## With skip_blank_lines = True
+        expected = pd.DataFrame([[4, 5, 6]], columns=['a', 'b', 'c'])
+
+        # GH 10728
+        # WHITESPACE_LINE
+        data = 'a,b,c\n4,5,6\n '
+        result = self.read_csv(StringIO(data))
+        tm.assert_frame_equal(result, expected)
+
+        # GH 10548
+        # EAT_LINE_COMMENT
+        data = 'a,b,c\n4,5,6\n#comment'
+        result = self.read_csv(StringIO(data), comment='#')
+        tm.assert_frame_equal(result, expected)
+
+        # EAT_CRNL_NOP
+        data = 'a,b,c\n4,5,6\n\r'
+        result = self.read_csv(StringIO(data))
+        tm.assert_frame_equal(result, expected)
+
+        # EAT_COMMENT
+        data = 'a,b,c\n4,5,6#comment'
+        result = self.read_csv(StringIO(data), comment='#')
+        tm.assert_frame_equal(result, expected)
+
+        # SKIP_LINE
+        data = 'a,b,c\n4,5,6\nskipme'
+        result = self.read_csv(StringIO(data), skiprows=[2])
+        tm.assert_frame_equal(result, expected)
+
+        ## With skip_blank_lines = False
+
+        # EAT_LINE_COMMENT
+        data = 'a,b,c\n4,5,6\n#comment'
+        result = self.read_csv(StringIO(data), comment='#', skip_blank_lines=False)
+        expected = pd.DataFrame([[4, 5, 6]], columns=['a', 'b', 'c'])
+        tm.assert_frame_equal(result, expected)
+
+        # IN_FIELD
+        data = 'a,b,c\n4,5,6\n '
+        result = self.read_csv(StringIO(data), skip_blank_lines=False)
+        expected = pd.DataFrame([['4', 5, 6], [' ', None, None]], columns=['a', 'b', 'c'])
+        tm.assert_frame_equal(result, expected)
+
+        # EAT_CRNL
+        data = 'a,b,c\n4,5,6\n\r'
+        result = self.read_csv(StringIO(data), skip_blank_lines=False)
+        expected = pd.DataFrame([[4, 5, 6], [None, None, None]], columns=['a', 'b', 'c'])
+        tm.assert_frame_equal(result, expected)
+
+        ## Should produce exceptions
+
+        # ESCAPED_CHAR
+        data = "a,b,c\n4,5,6\n\\"
+        self.assertRaises(Exception, self.read_csv, StringIO(data), escapechar='\\')
+
+        # ESCAPE_IN_QUOTED_FIELD
+        data = 'a,b,c\n4,5,6\n"\\'
+        self.assertRaises(Exception, self.read_csv, StringIO(data), escapechar='\\')
+
+        # IN_QUOTED_FIELD
+        # Python 2.6 won't throw an exception for this case (see http://bugs.python.org/issue16013)
+        tm._skip_if_python26()
+        data = 'a,b,c\n4,5,6\n"'
+        self.assertRaises(Exception, self.read_csv, StringIO(data), escapechar='\\')
+
 
 
 class TestPythonParser(ParserTests, tm.TestCase):

pandas/src/parser/tokenizer.c

@@ -1413,9 +1413,9 @@ int tokenize_whitespace(parser_t *self, size_t line_limit)
                     self->state = EAT_CRNL;
                 break;
             } else if (IS_WHITESPACE(c)) {
-                /*if (self->skip_empty_lines)
+                if (self->skip_empty_lines)
                     self->state = WHITESPACE_LINE;
-                    else*/
+                else
                     self->state = EAT_WHITESPACE;
                 break;
             } else if (c == self->commentchar) {
@@ -1643,34 +1643,44 @@ int tokenize_whitespace(parser_t *self, size_t line_limit)
 
 static int parser_handle_eof(parser_t *self) {
     TRACE(("handling eof, datalen: %d, pstate: %d\n", self->datalen, self->state))
-    if (self->datalen == 0 && (self->state != START_RECORD)) {
-        // test cases needed here
-        // TODO: empty field at end of line
-        TRACE(("handling eof\n"));
 
-        if (self->state == IN_FIELD || self->state == START_FIELD) {
-            if (end_field(self) < 0)
-                return -1;
-        } else if (self->state == QUOTE_IN_QUOTED_FIELD) {
-            if (end_field(self) < 0)
-                return -1;
-        } else if (self->state == IN_QUOTED_FIELD) {
-            self->error_msg = (char*) malloc(100);
-            sprintf(self->error_msg, "EOF inside string starting at line %d",
-                    self->file_lines);
-            return -1;
-        }
+    if (self->datalen != 0)
+        return -1;
 
-        if (end_line(self) < 0)
+    switch (self->state) {
+    case START_RECORD:
+    case WHITESPACE_LINE:
+    case EAT_CRNL_NOP:
+    case EAT_LINE_COMMENT:
+        return 0;
+
+    case ESCAPE_IN_QUOTED_FIELD:
+    case IN_QUOTED_FIELD:
+        self->error_msg = (char*)malloc(100);
+        sprintf(self->error_msg, "EOF inside string starting at line %d",
+                self->file_lines);
+        return -1;
+
+    case ESCAPED_CHAR:
+        self->error_msg = (char*)malloc(100);
+        sprintf(self->error_msg, "EOF following escape character");
+        return -1;
+
+    case IN_FIELD:
+    case START_FIELD:
+    case QUOTE_IN_QUOTED_FIELD:
+        if (end_field(self) < 0)
             return -1;
+        break;
 
-        return 0;
-    }
-    else if (self->datalen == 0 && (self->state == START_RECORD)) {
-        return 0;
+    default:
+        break;
     }
 
-    return -1;
+    if (end_line(self) < 0)
+        return -1;
+    else
+        return 0;
 }
 
 int parser_consume_rows(parser_t *self, size_t nrows) {

pandas/util/testing.py

@@ -241,6 +241,12 @@ def _skip_if_no_cday():
         raise nose.SkipTest("CustomBusinessDay not available.")
 
 
+def _skip_if_python26():
+    if sys.version_info[:2] == (2, 6):
+        import nose
+        raise nose.SkipTest("skipping on python2.6")
+
+
 #------------------------------------------------------------------------------
 # locale utilities