Getting both levels of a multi-index to re-index a dataframe

Question

I want to get both levels of a multi-index dataframe so I can re-index a dataframe based on this.

Take a dataframe:

import pandas as pd
import numpy as np

dates = pd.date_range('20070101',periods=3200)
df = pd.DataFrame(data=np.random.randint(0,100,(3200,1)), columns =list('A'))
df['date'] = dates
df = df[['date','A']]

Apply season function to the datetime index

def get_season(row):
    if row['date'].month >= 3 and row['date'].month <= 5:
        return '2'
    elif row['date'].month >= 6 and row['date'].month <= 8:
        return '3'
    elif row['date'].month >= 9 and row['date'].month <= 11:
        return '4'
    else:
        return '1'

Apply the function

df['Season'] = df.apply(get_season, axis=1)

Create a 'Year' column for indexing

df['Year'] = df['date'].dt.year

Multi-index by Year and Season

df = df.set_index(['Year', 'Season'], inplace=False)

Group the data

df2 = df['A'].groupby(level=['Year','Season']).mean()

When I query this for the first level:

df2.index.get_level_values(0)

I get the years:

Out[4]: 
Int64Index([2007, 2007, 2007, 2007, 2008, 2008, 2008, 2008, 2009, 2009, 2009,
        2009, 2010, 2010, 2010, 2010, 2011, 2011, 2011, 2011, 2012, 2012,
        2012, 2012, 2013, 2013, 2013, 2013, 2014, 2014, 2014, 2014, 2015,
        2015, 2015, 2015],
       dtype='int64', name=u'Year')

and the second level:

df2.index.get_level_values(1)

I get the seasons:

Out[6]: 
Index([u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4',
   u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4',
   u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4', u'1', u'2', u'3', u'4'],
  dtype='object', name=u'Season')

But I want both years and seasons associated with eachother - so I can re-index a dataframe based on both year and season, both levels of the multi-index.

That is - I want ([2007;1 , 2007;2 , 2007;3]) etc.

Is this possible to do? Thanks.

Answer 1

>>> df2.index.tolist()
[(2007, '1'),
 (2007, '2'),
 (2007, '3'),
 (2007, '4'),
 (2008, '1'),
 (2008, '2'),
 (2008, '3'),
 (2008, '4'),
...
]