datetime to string with series in pandas

There is no .str accessor for datetimes and you can’t do .astype(str) either.

Instead, use .dt.strftime:

>>> series = pd.Series(['20010101', '20010331'])
>>> dates = pd.to_datetime(series, format="%Y%m%d")
>>> dates.dt.strftime('%Y-%m-%d')
0    2001-01-01
1    2001-03-31
dtype: object

See the docs on customizing date string formats here: strftime() and strptime() Behavior.

For old pandas versions <0.17.0, one can instead can call .apply with the Python standard library’s datetime.strftime:

>>> dates.apply(lambda x: x.strftime('%Y-%m-%d'))
0    2001-01-01
1    2001-03-31
dtype: object