calculate datetime-difference in years, months, etc. in a new pandas dataframe column

Question

I have a pandas dataframe looking like this:

Name    start        end
A       2000-01-10   1970-04-29

I want to add a new column providing the

Answer 1

I think this is the most 'pandas' way to do it, without using any for loops or defining external functions:

>>> df = pd.DataFrame({'Name': ['A'], 'start': [datetime(2000, 1, 10)], 'end': [datetime(1970, 4, 29)]})
>>> df['diff'] = map(lambda td: datetime(1, 1, 1) + td, list(df['start'] - df['end']))
>>> df['diff'] = df['diff'].apply(lambda d: '{0}y{1}m'.format(d.year - 1, d.month - 1))
>>> df
  Name        end      start   diff
0    A 1970-04-29 2000-01-10  29y8m

Had to use map instead of apply because of pandas' timedelda64, which doesn't allow a simple addition to a datetime object.