Convert YYYYMMDD to YYYY-MM-DD

From raju

Python

    >>> from datetime import datetime
    >>> dt = 20140716
    >>> datetime.strptime(str(dt), '%Y%m%d').strftime('%Y-%m-%d')
    '2014-07-16'
    

To do the same thing for a column in a dataframe

    >>> import pandas as pd
    >>> from datetime import datetime
    >>> name = ['foo', 'bar']; date = ['20160824', '20160825']; name_date = pd.DataFrame({'name': name, 'date': date}); name_date
           date name
    0  20160824  foo
    1  20160825  bar
    
    >>> name_date['date'] = pd.to_datetime(name_date['date'], format='%Y%m%d').dt.strftime("%Y-%m-%d"); name_date
             date name
    0  2016-08-24  foo
    1  2016-08-25  bar
    

Tested with

    >python --version
    Python 3.4.4 :: Continuum Analytics, Inc.
    

Ref:- http://importpython.blogspot.com/2014/07/how-to-convert-date-formats-from.html