BUG FIX: cartesian_product now converts all arguments to ndarrays

Fixes GitHub issue pandas-dev#6439.

Author: shoyer

pandas/tools/tests/test_util.py

@@ -6,6 +6,7 @@
 import numpy as np
 from numpy.testing import assert_equal
 
+import pandas
 import pandas.util.testing as tm
 from pandas.tools.util import cartesian_product
 
@@ -23,6 +24,13 @@ def test_simple(self):
                     np.array([ 1, 22,  1, 22,  1, 22])]
         assert_equal(result, expected)
 
+    def test_datetimeindex(self):
+        # regression test for GitHub issue #6439
+        x = pandas.date_range('2000-01-01', periods=2)
+        result = [pandas.Index(y).day for y in cartesian_product([x, x])]
+        expected = [np.array([1, 1, 2, 2]), np.array([1, 2, 1, 2])]
+        assert_equal(result, expected)
+
 
 class TestLocaleUtils(tm.TestCase):
 

pandas/tools/util.py

@@ -29,7 +29,7 @@ def cartesian_product(X):
 
     b = cumprodX[-1] / cumprodX
 
-    return [np.tile(np.repeat(x, b[i]),
+    return [np.tile(np.repeat(np.asarray(x), b[i]),
                     np.product(a[i]))
                for i, x in enumerate(X)]