Creating empty pandas dataframe with Multi-Index

Question

I'm trying to create an empty pandas.Dataframe with a Multi-Index that I can later fill columnwise with my data. I've looked at other answers (here and here), but they all work with data that does not fill in columnwise, or that is somehow connected in the different columns.

The information I want to be contained in the Multi-Index looks like this:

GCM_list = ['BCC-CSM2-MR', 'CAMS-CSM1-0', 'CESM2', 'CESM2-WACCM', 'CMCC-CM2-SR5', 'EC-Earth3', 'EC-Earth3-Veg', 'FGOALS-f3-L', 'GFDL-ESM4', 'INM-CM4-8', 'INM-CM5-0', 'MPI-ESM1-2-HR', 'MRI-ESM2-0', 'NorESM2-MM', 'TaiESM1']
SSP_list = ['SSP_126', 'SSP_245', 'SSP_370', 'SSP_585']
index_years = [2030, 2040, 2050, 2060, 2070, 2080, 2090, 2100]

And I want it to look somewhat like this (for the three first items in GCM_list):

               BCC-CSM2-MR                               CAMS-CSM1-0                                CESM2
     SSP_126  SSP_245  SSP_370  SSP_585      SSP_126  SSP_245  SSP_370  SSP_585       SSP_126  SSP_245  SSP_370  SSP_585
2030    |        |
2040    |        |
2050    V        V
2060    1        2
2070
2080
2090
2100

The "arrows" in the first two columns should represent how and in what order I want to fill the Dataframe after the Index is created - if that's important for this question.

I've tried building the index like this, but I'm not sure what to make of the result. How should I proceed? Is there a way to build this empty dataframe so that I can fill it column after column?

arrays = [GCM_list, SSP_list]
index = pd.MultiIndex.from_arrays(arrays, names=('GCM', 'SSP'))
>>> index
MultiIndex(levels=[[u'BCC-CSM2-MR', u'CAMS-CSM1-0', u'CESM2', u'CESM2-WACCM', u'CMCC-CM2-SR5', u'EC-Earth3', u'EC-Earth3-Veg', u'FGOALS-f3-L', u'GFDL-ESM4', u'INM-CM4-8', u'INM-CM5-0', u'MPI-ESM1-2-HR', u'MRI-ESM2-0', u'NorESM2-MM', u'TaiESM1'], [u'SSP_126', u'SSP_245', u'SSP_370', u'SSP_585']],
           labels=[[0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14], [0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3]],
           names=[u'GCM', u'SSP'])

jezrael · Accepted Answer · 2021-05-26 11:41:30Z

2

Use MultiIndex.from_product:

arrays = [GCM_list, SSP_list]
mux = pd.MultiIndex.from_product(arrays, names=('GCM', 'SSP'))

df = pd.DataFrame(columns=mux, index=index_years)

answered May 26, 2021 at 11:41

jezrael

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