ENH: more flexibility in parser dtype specification. close #1858

Author: wesm

pandas/io/tests/test_cparser.py

@@ -258,10 +258,20 @@ def _make_reader(**kwds):
 
         reader = _make_reader(dtype={'one': 'u1', 1: 'S1'})
         result = reader.read()
-
         self.assert_(result[0].dtype == 'u1')
         self.assert_(result[1].dtype == 'S1')
 
+        reader = _make_reader(dtype={'one': np.uint8, 1: object})
+        result = reader.read()
+        self.assert_(result[0].dtype == 'u1')
+        self.assert_(result[1].dtype == 'O')
+
+        reader = _make_reader(dtype={'one': np.dtype('u1'),
+                                     1: np.dtype('O')})
+        result = reader.read()
+        self.assert_(result[0].dtype == 'u1')
+        self.assert_(result[1].dtype == 'O')
+
     def test_usecols(self):
         data = """\
 a,b,c

pandas/src/parser.pyx

@@ -820,8 +820,12 @@ cdef class TextReader:
                     col_dtype = self.dtype
 
             if col_dtype is not None:
-                if isinstance(col_dtype, np.dtype):
-                    col_dtype = col_dtype.str
+                if not isinstance(col_dtype, basestring):
+                    if isinstance(col_dtype, np.dtype):
+                        col_dtype = col_dtype.str
+                    else:
+                        col_dtype = np.dtype(col_dtype).str
+
                 return self._convert_with_dtype(col_dtype, i, start, end,
                                                 na_filter, na_hashset)