Fix period range (#5393)

* Converting period to timestamp

* Added unit test

* Convert in max_range instead

holoviews/core/data/pandas.py

@@ -1,8 +1,3 @@
-try:
-    import itertools.izip as zip
-except ImportError:
-    pass
-
 import numpy as np
 import pandas as pd
 

holoviews/core/util.py

@@ -922,7 +922,10 @@ def max_range(ranges, combined=True):
                           for r in values for v in r):
                 converted = []
                 for l, h in values:
-                    if isinstance(l, datetime_types) and isinstance(h, datetime_types):
+                    if isinstance(l, pd.Period) and isinstance(h, pd.Period):
+                        l = l.to_timestamp().to_datetime64()
+                        h = h.to_timestamp().to_datetime64()
+                    elif isinstance(l, datetime_types) and isinstance(h, datetime_types):
                         l, h = (pd.Timestamp(l).to_datetime64(),
                                 pd.Timestamp(h).to_datetime64())
                     converted.append((l, h))

holoviews/tests/core/test_utils.py

@@ -332,6 +332,10 @@ def test_max_range2(self):
         self.assertTrue(math.isnan(lower))
         self.assertTrue(math.isnan(upper))
 
+    def test_max_range3(self):
+        periods = [(pd.Period("1990", freq="M"), pd.Period("1991", freq="M"))]
+        expected = (np.datetime64("1990", 'ns'), np.datetime64("1991", 'ns'))
+        self.assertEqual(max_range(periods), expected)
 
 
 class TestWrapTupleStreams(unittest.TestCase):