Concatenate/combine two columns into one for Pandas dataframe when axis = 0

Question

I have dataframe:

d_test = {
    'c1' : ['a', 'b', np.nan, 'c'],
    'c2' : ['d', np.nan, 'e', 'f'],
    'test': [1,2,3,4],
}
df_test = pd.DataFrame(d_test)

And I want to concatenate columns c1 and c2 in one and have following resulted dataframe:

a 1
b 2
c 4
d 1
e 3
f 4

I tired to use

pd.concat([df_test.c1 , df_test.c2], axis = 0)

to generate such a column but have no idea how to keep 'test' column as well during concationation.

Panda Kim · Accepted Answer · 2022-12-08 03:05:14Z

1

use melt

df_test.melt('test').dropna()[['value', 'test']]

result:

    value   test
0   a       1
1   b       2
3   c       4
4   d       1
6   e       3
7   f       4

answered Dec 8, 2022 at 3:05

Panda Kim

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