ENH: support .strftime for datetimelikes (closes #10086)

Author: mortada

pandas/tests/test_series.py

@@ -83,7 +83,7 @@ def test_dt_namespace_accessor(self):
         ok_for_period = ok_for_base + ['qyear']
         ok_for_dt = ok_for_base + ['date','time','microsecond','nanosecond', 'is_month_start', 'is_month_end', 'is_quarter_start',
                                    'is_quarter_end', 'is_year_start', 'is_year_end', 'tz']
-        ok_for_dt_methods = ['to_period','to_pydatetime','tz_localize','tz_convert', 'normalize']
+        ok_for_dt_methods = ['to_period','to_pydatetime','tz_localize','tz_convert', 'normalize', 'strftime']
         ok_for_td = ['days','seconds','microseconds','nanoseconds']
         ok_for_td_methods = ['components','to_pytimedelta']
 
@@ -135,6 +135,16 @@ def compare(s, name):
             expected = Series(DatetimeIndex(s.values).tz_localize('UTC').tz_convert('US/Eastern'),index=s.index)
             tm.assert_series_equal(result, expected)
 
+        s = Series(date_range('20130101', periods=5))
+        result = s.dt.strftime('%Y/%m/%d')
+        expected = ['2013/01/01', '2013/01/02', '2013/01/03', '2013/01/04', '2013/01/05']
+        self.assertEqual(result, expected)
+
+        s.iloc[0] = pd.NaT
+        result = s.dt.strftime('%Y/%m/%d')
+        expected = ['NaT', '2013/01/02', '2013/01/03', '2013/01/04', '2013/01/05']
+        self.assertEqual(result, expected)
+
         # timedeltaindex
         for s in [Series(timedelta_range('1 day',periods=5),index=list('abcde')),
                   Series(timedelta_range('1 day 01:23:45',periods=5,freq='s')),

pandas/tseries/common.py

@@ -121,6 +121,21 @@ class DatetimeProperties(Properties):
     def to_pydatetime(self):
         return self.values.to_pydatetime()
 
+    def strftime(self, date_format):
+        """
+        Return a list of formmatted strings specified by date_format
+
+        Parameters
+        ----------
+        date_format : str
+            date format string (e.g. "%Y-%m-%d")
+
+        Returns
+        -------
+        a list formatted strings
+        """
+        return self.values.format(date_format=date_format)
+
 DatetimeProperties._add_delegate_accessors(delegate=DatetimeIndex,
                                            accessors=DatetimeIndex._datetimelike_ops,
                                            typ='property')