Fix for pandas-dev#12048

Author: Sereger13

pandas/io/parsers.py

@@ -4,6 +4,7 @@
 from __future__ import print_function
 from pandas.compat import range, lrange, StringIO, lzip, zip, string_types, map
 from pandas import compat
+from collections import defaultdict
 import re
 import csv
 import warnings
@@ -2264,6 +2265,8 @@ def _get_empty_meta(columns, index_col, index_names, dtype=None):
     if dtype is None:
         dtype = {}
     else:
+        if not isinstance(dtype, dict):
+            dtype = defaultdict(lambda: dtype)
         # Convert column indexes to column names.
         dtype = dict((columns[k] if com.is_integer(k) else k, v)
                      for k, v in compat.iteritems(dtype))

pandas/tests/frame/test_to_csv.py

@@ -1108,3 +1108,9 @@ def test_to_csv_with_dst_transitions(self):
             df.to_pickle(path)
             result = pd.read_pickle(path)
             assert_frame_equal(result, df)
+
+    def test_to_csv_empty_frame(self):
+        # GH12048
+        actual = read_csv(StringIO('A,B'), dtype=str)
+        expected = pd.DataFrame({'A': [], 'B': []}, dtype=str).reset_index(drop=True)
+        assert_frame_equal(actual, expected, check_names=False, check_index_type=False)