Selecting Sublevels Of Multiindex Columns In Pandas

I generate a multiindex dataframe like this example import pandas as pd import numpy as np iterables = [ ['co1', 'co2', 'co3', 'co4'], ['age','weight'] ] multi = pd.MultiIndex.fro

Solution 1:

IIUC then you can use loc and pass a tuple consisting of a slice and column label to access the col of interest at that level:

In [59]:
iterables = [ ['co1', 'co2', 'co3', 'co4'], ['age','weight'] ]
multi = pd.MultiIndex.from_product(iterables, names= ["Spread", "attribute"])
df = pd.DataFrame(np.random.rand(80).reshape(10,8),index = range(0,10), columns = multi)
df

Out[59]:
Spread          co1                 co2                 co3            \
attribute       age    weight       age    weight       age    weight   
00.6009470.5095370.6055380.4960020.2152060.07507910.1529560.9228320.1677880.0247610.6223780.98303020.7124780.6037980.4070140.6254740.4455920.90324030.4205690.5766040.2200970.4016240.9294640.51202640.2730880.0323030.6075770.8362310.7518450.18152250.8596990.2747600.4568120.6661090.3499610.23789460.6327540.6032520.1574160.2215760.0683550.12186470.0905950.0355260.6982620.5257700.7926180.22060180.6702360.8051950.3106800.1004640.8752990.85323890.0205010.4052450.4476140.9993400.6596160.709312   

Spread          co4            
attribute       age    weight  
00.2974210.41573010.2352590.15601420.3657620.19829930.6954310.47845740.3316570.33843650.9438100.09799960.6387200.03374770.6469690.47531680.6232250.02497690.0234940.959514  

In [61]:
df.loc[1,(slice(None),'weight')]

Out[61]:
Spread  attribute
co1     weight       0.922832
co2     weight       0.024761
co3     weight       0.983030
co4     weight       0.156014
Name: 1, dtype: float64

To explain the syntax:

df.loc[1,(slice(None),'weight')]

So the first param is just your index lave, the second param is a tuple consisting of a slice and a col label, the first member being slice(None) selects all cols 'col1' to 'col4' in effect, then the second param selects at the next level cols that match the label 'weight'