[FIXED] how to pass *args in df.apply()

Issue

I have a function which I want to be able to apply on variable number of columns based on the input.

def split_and_combine(row, *args, delimiter=';'):
    combined = []
    for a in args:
        if not row[a]:
            combined.extend(row[a].split(delimiter))

    combined = list(set(combined))
    return combined

But I'm not sure how to apply this function to the df, because of the *args. I'm not very familiar with *args and *kwargs in python. I tried using partial and set axis=1 as below but get the TypeError below.

df['combined'] = df.apply(partial(split_and_combine, ['col1','col2']),
                          axis=1)

TypeError: ('list indices must be integers or slices, not Series', 'occurred at index 0')

A dummy example for the above code. I want to be able to pass in flexible number of columns to combine:

Index   col1        col2            combined
0      John;Mary    Sam;Bill;Eva    John;Mary;Sam;Bill;Eva
1      a;b;c        a;d;f           a;b;c;d;f

Thanks! If there's a better for doing this without df.apply. Please feel free to comment!

Solution

df.apply docs

args : tuple

Positional arguments to pass to func in addition to the array/series.

**kwds

Additional keyword arguments to pass as keywords arguments to func.

df.apply(split_and_combine, args=('col1', 'col2'), axis=1)

btw you might have some bugs in your function:

def split_and_combine(row, *args, delimiter=';'):
    combined = []
    for a in args:
        if row[a]:
            combined.extend(row[a].split(delimiter))
    combined = list(set(combined))
    return delimiter.join(combined)

Answered By - Asish M.

Answer Checked By - Terry (PHPFixing Volunteer)