Convert pandas series to string and datetime object

[zljubisic at gmail.com]

I have sliced the pandas dataframe 

end_date = df[-1:]['end']

type(end_date)
Out[4]: pandas.core.series.Series

end_date
Out[3]: 
48173   2017-09-20 04:47:59
Name: end, dtype: datetime64[ns]

1.	How to get rid of index value 48173 and get only "2017-09-20 04:47:59" string? I have to call REST API with "2017-09-20 04:47:59" as a parameter, so I have to get string from pandas datetime64 series.
2.	How to get rid of index value 48173 and get only datetime object [something like datetime.datetime.strptime('2017-09-20 04:47:59', '%Y-%m-%d %H:%M:%S')]. Later I will have to check if '2017-09-20 04:47:59' < datetime.datetime(2017,1,9)

How to do these conversions?