python - How to concatenate multiple column values into a single column in Pandas dataframe

Question

This question is same to this posted earlier. I want to concatenate three columns instead of concatenating two columns:

Here is the combining two columns:

df = DataFrame({'foo':['a','b','c'], 'bar':[1, 2, 3], 'new':['apple', 'banana', 'pear']})

df['combined']=df.apply(lambda x:'%s_%s' % (x['foo'],x['bar']),axis=1)

df
    bar foo new combined
0   1   a   apple   a_1
1   2   b   banana  b_2
2   3   c   pear    c_3

I want to combine three columns with this command but it is not working, any idea?

df['combined']=df.apply(lambda x:'%s_%s' % (x['bar'],x['foo'],x['new']),axis=1)

Answer 1

Another solution using DataFrame.apply(), with slightly less typing and more scalable when you want to join more columns:

cols = ['foo', 'bar', 'new']
df['combined'] = df[cols].apply(lambda row: '_'.join(row.values.astype(str)), axis=1)