How to get Pandas multiindex column names as a list

Question

I have the following CSV data:

id,gene,celltype,stem,stem,stem,bcell,bcell,tcell
id,gene,organs,bm,bm,fl,pt,pt,bm
134,foo,about_foo,20,10,11,23,22,79
222,bar,about_bar,17,13,55,12,13,88

And I can successfully generalize them as follows:

import pandas as pd
df = pd.read_csv("http://dpaste.com/1X74TNP.txt",header=None,index_col=[1,2]).iloc[:, 1:]

df.columns = pd.MultiIndex.from_arrays(df.ix[:2].values)
df = df.ix[2:].astype(int)
df.index.names = ['cell', 'organ']
df = df.reset_index('organ', drop=True)

result = df.groupby(level=[0, 1], axis=1).mean()
result = result.stack().replace(np.nan, 0).unstack()
result = result.swaplevel(0,1, axis=1).sort_index(axis=1)

What does it look like:

In [341]: result
Out[341]:
        bm               fl               pt
     bcell stem tcell bcell stem tcell bcell stem tcell
cell
foo      0   15    79     0   11     0  22.5    0     0
bar      0   15    88     0   55     0  12.5    0     0

My question is: resulthow to get the index of a first level column in a list view:

['bm','fl','pt']

Answer 1

result.columnsreturns a pandas.core.index.MultiIndexthat has a level attribute.

list(result.columns.levels[0])

returns

['bm', 'fl', 'pt']

Answer 2

Alternatively, you can use columnns.get_level_values ​​(level)

 >>> result.columns.get_level_values(0).unique()
    array(['bm', 'fl', 'pt'], dtype=object)
 >>> list(result.columns.get_level_values(0))
    ['bm', 'bm', 'bm', 'fl', 'fl', 'fl', 'pt', 'pt', 'pt']