How to filter pandas dataframe to select list of column-CodePudding

I have a dataframe with 100 columns and I want to select list of variables

ID           A                  B                   C
    0  day1  day10  Δday   day1 day10  Δday    day1 day10  Δday
1   1  1.0   2.0    1.0    1.5  2.5    1.0     3.0  2.0    -1.0
2   2  3.0   5.0    2.0    1.0  2.5    1.5     3.0  5.0     2.0
3   3  2.5   3.5    1.0    1.5  2.9    1.4     3.5  4.0     0.5
............................................................
............................................................

df.columns

Index(['A', 'Unnamed: 1', 'Unnamed: 2', 'B', 'Unnamed: 4', 'Unnamed: 5', 'C','Unnamed: 7', 'Unnamed: 8'],
      dtype='object')

How do I filter which should yield the output as:

A      B      C
Δday   Δday   Δday
1.0    1.0    -1.0
2.0    1.5     2.0
1.0    1.4     0.5

I looked at Pandas' documentation and tried filter regex, iloc but did not succeed.

CodePudding user response：

Try slice(None) to select any column at first level:

>>> df.loc[:, (slice(None), 'Δday')]

     A    B    C
  Δday Δday Δday
0  1.0  1.0 -1.0
1  2.0  1.5  2.0
2  1.0  1.4  0.5

To know more: Using slicers

Update

Tried to applied and getting TypeError: unhashable type: 'slice'

Your problem is because you don't use read_excel correctly. Your second row is not a column header but a simple row. Try to specify the header:

df = pd.read_excel('data.xlsx', ..., header=[0, 1])