Pandas: pass a large number of columns to a function using a list containing the column names

Is it possible to store the names of certain columns in a list? Then use that list to pass those columns’ values into a function using apply().

Suppose I was passing 10 columns to a function (df.A to df.J) and I had a list containing the names of the columns A through J.

df['H'] = df.apply(lambda x: myfunction(x.A, x.B, x.C, x.D ... ), axis=1)

How could I write that using the list instead of having to type out each column?

>Solution :

You can pass columns names in list cols and then * for unpacking:

np.random.seed(26)

df = pd.DataFrame(np.random.randint(10, size=(3,3)), columns=list('ABC'))
print (df)
   A  B  C
0  5  6  0
1  1  6  3
2  0  4  2

def myfunction(a,b,c):
    return (a,b,c)

cols = ['A','B','C']
df['out'] = df[cols].apply(lambda x: myfunction(*x), axis=1)
print (df)
   A  B  C        out
0  5  6  0  (5, 6, 0)
1  1  6  3  (1, 6, 3)
2  0  4  2  (0, 4, 2)