How to include end date in pandas date_range method?

Question

From pd.date_range(\'2016-01\', \'2016-05\', freq=\'M\', ).strftime(\'%Y-%m\'), the last month is 2016-04, but I was expecting it to be 2016

Answer 1

The explanation for this issue is that the function pd.to_datetime() converts a '%Y-%m' date string by default to the first of the month datetime, or '%Y-%m-01':

>>> pd.to_datetime('2016-05')
Timestamp('2016-05-01 00:00:00')
>>> pd.date_range('2016-01', '2016-02')
DatetimeIndex(['2016-01-01', '2016-01-02', '2016-01-03', '2016-01-04',
               '2016-01-05', '2016-01-06', '2016-01-07', '2016-01-08',
               '2016-01-09', '2016-01-10', '2016-01-11', '2016-01-12',
               '2016-01-13', '2016-01-14', '2016-01-15', '2016-01-16',
               '2016-01-17', '2016-01-18', '2016-01-19', '2016-01-20',
               '2016-01-21', '2016-01-22', '2016-01-23', '2016-01-24',
               '2016-01-25', '2016-01-26', '2016-01-27', '2016-01-28',
               '2016-01-29', '2016-01-30', '2016-01-31', '2016-02-01'],
              dtype='datetime64[ns]', freq='D')

Then everything follows from that. Specifying freq='M' includes month ends between 2016-01-01 and 2016-05-01, which is the list you receive and excludes 2016-05-31. But specifying month starts 'MS' like the second answer provides, includes 2016-05-01 as it falls within the range. pd.date_range() default behavior isn't like the range method since ends are included. From the docs:

closed controls whether to include start and end that are on the boundary. The default includes boundary points on either end.