ENH: add weekday_name to DatetimeIndex and .dt #11128
Description
These names exist already in pd.tslib (as the below weedays calc), should just create them as a variable so can import it directly here.
In [1]: import calendar In [25]: s = pd.Series(list(range(10)), pd.date_range('2015-09-01', '2015-09-10')) In [26]: s2 = s.to_frame('value').assign(weekday=Series(s.index.weekday).map(Series(weekdays)).values) In [27]: weekdays = [calendar.day_name[i].lower() for i in range(7)] In [28]: s2 = s.to_frame('value').assign(weekday=Series(s.index.weekday).map(Series(weekdays)).values) In [29]: s2 Out[29]: value weekday 2015-09-01 0 tuesday 2015-09-02 1 wednesday 2015-09-03 2 thursday 2015-09-04 3 friday 2015-09-05 4 saturday 2015-09-06 5 sunday 2015-09-07 6 monday 2015-09-08 7 tuesday 2015-09-09 8 wednesday 2015-09-10 9 thursday