API: Add PeriodIndex.resolution

doc/source/v0.15.0.txt

@@ -117,6 +117,8 @@ Enhancements
 - Added support for bool, uint8, uint16 and uint32 datatypes in ``to_stata`` (:issue:`7097`, :issue:`7365`)
 
 
+- ``PeriodIndex`` supports ``resolution`` as the same as ``DatetimeIndex`` (:issue:`7708`)
+
 
 
 

pandas/core/base.py

@@ -498,3 +498,17 @@ def __unicode__(self):
         summary += self._format_footer()
         return summary
 
+    @cache_readonly
+    def _resolution(self):
+        from pandas.tseries.frequencies import Resolution
+        return Resolution.get_reso_from_freq(self.freqstr)
+
+    @cache_readonly
+    def resolution(self):
+        """
+        Returns day, hour, minute, second, millisecond or microsecond
+        """
+        from pandas.tseries.frequencies import get_reso_string
+        return get_reso_string(self._resolution)
+
+

pandas/tests/test_base.py

@@ -605,6 +605,14 @@ def test_representation(self):
                 result = getattr(idx, func)()
                 self.assertEqual(result, expected)
 
+    def test_resolution(self):
+        for freq, expected in zip(['A', 'Q', 'M', 'D', 'H', 'T', 'S', 'L', 'U'],
+                                  ['day', 'day', 'day', 'day',
+                                   'hour', 'minute', 'second', 'millisecond', 'microsecond']):
+            for tz in [None, 'Asia/Tokyo', 'US/Eastern']:
+                idx = pd.date_range(start='2013-04-01', periods=30, freq=freq, tz=tz)
+                self.assertEqual(idx.resolution, expected)
+
 
 class TestPeriodIndexOps(Ops):
     _allowed = '_allow_period_index_ops'
@@ -729,6 +737,14 @@ def test_representation(self):
                 result = getattr(idx, func)()
                 self.assertEqual(result, expected)
 
+    def test_resolution(self):
+        for freq, expected in zip(['A', 'Q', 'M', 'D', 'H', 'T', 'S', 'L', 'U'],
+                                  ['day', 'day', 'day', 'day',
+                                   'hour', 'minute', 'second', 'millisecond', 'microsecond']):
+
+            idx = pd.period_range(start='2013-04-01', periods=30, freq=freq)
+            self.assertEqual(idx.resolution, expected)
+
 
 if __name__ == '__main__':
     import nose

pandas/tseries/frequencies.py

@@ -45,7 +45,9 @@ class Resolution(object):
     RESO_HR: 'hour',
     RESO_DAY: 'day'}
 
-    _reso_period_map = {
+    _str_reso_map = dict([(v, k) for k, v in compat.iteritems(_reso_str_map)])
+
+    _reso_freq_map = {
     'year': 'A',
     'quarter': 'Q',
     'month': 'M',
@@ -57,13 +59,28 @@ class Resolution(object):
     'microsecond': 'U',
     'nanosecond': 'N'}
 
+    _freq_reso_map = dict([(v, k) for k, v in compat.iteritems(_reso_freq_map)])
+
     @classmethod
     def get_str(cls, reso):
         return cls._reso_str_map.get(reso, 'day')
 
+    @classmethod
+    def get_reso(cls, resostr):
+        return cls._str_reso_map.get(resostr, cls.RESO_DAY)
+
     @classmethod
     def get_freq(cls, resostr):
-        return cls._reso_period_map[resostr]
+        return cls._reso_freq_map[resostr]
+
+    @classmethod
+    def get_str_from_freq(cls, freq):
+        return cls._freq_reso_map.get(freq, 'day')
+
+    @classmethod
+    def get_reso_from_freq(cls, freq):
+        return cls.get_reso(cls.get_str_from_freq(freq))
+
 
 def get_reso_string(reso):
     return Resolution.get_str(reso)
@@ -593,7 +610,7 @@ def _period_alias_dictionary():
 
 
 def _infer_period_group(freqstr):
-    return _period_group(Resolution._reso_period_map[freqstr])
+    return _period_group(Resolution._reso_freq_map[freqstr])
 
 
 def _period_group(freqstr):

pandas/tseries/index.py

@@ -1536,14 +1536,6 @@ def is_normalized(self):
         """
         return tslib.dates_normalized(self.asi8, self.tz)
 
-    @cache_readonly
-    def resolution(self):
-        """
-        Returns day, hour, minute, second, or microsecond
-        """
-        reso = self._resolution
-        return get_reso_string(reso)
-
     @cache_readonly
     def _resolution(self):
         return tslib.resolution(self.asi8, self.tz)