pandas: best way to select all columns whose names start with X

Question

I have a DataFrame:

import pandas as pd
import numpy as np

df = pd.DataFrame({\'foo.aa\': [1, 2.1, np.nan, 4.7, 5.6, 6.8],
                   \'foo.fighters         


        

Answer 1

My solution. It may be slower on performance:

a = pd.concat(df[df[c] == 1] for c in df.columns if c.startswith('foo'))
a.sort_index()


   bar.baz  foo.aa  foo.bars  foo.fighters  foo.fox foo.manchu nas.foo
0      5.0     1.0         0             0        2         NA      NA
1      5.0     2.1         0             1        4          0       0
2      6.0     NaN         0           NaN        1          0       1
5      6.8     6.8         1             0        5          0       0