Pandas - combine column values into a list in a new column
I have a Python Pandas dataframe df:
d=[['hello',1,'GOOD','long.kw'],
[1.2,'chipotle',np.nan,'bingo'],
['various',np.nan,3000,123.456]]
t=pd.DataFrame(data=d, columns=['A','B','C','D'])
which looks like this:
print(t)
A B C D
0 hello 1 GOOD long.kw
1 1.2 chipotle NaN bingo
2 various NaN 3000 123.456
I am trying to create a new column which is a list of the values in A, B, C, and D. So it would look like this:
t['combined']
Out[125]:
0 [hello, 1, GOOD, long.kw]
1 [1.2, chipotle, nan, bingo]
2 [various, nan, 3000, 123.456]
Name: combined, dtype: object
I am trying this code:
t['combined'] = t.apply(lambda x: list([x['A'],
x['B'],
x['C'],
x['D']]),axis=1)
Which returns this error:
ValueError: Wrong number of items passed 4, placement implies 1
What is puzzling to me is if remove one of the columns that I want to put in the list (or add another column to the dataframe that I DON'T add to the list), my code works.
For instance, run this code:
t['combined'] = t.apply(lambda x: list([x['A'],
x['B'],
x['D']]),axis=1)
Returns this which is perfect if I only wanted the 3 columns:
print(t)
A B C D combined
0 hello 1 GOOD long.kw [hello, 1, long.kw]
1 1.2 chipotle NaN bingo [1.2, chipotle, bingo]
2 various NaN 3000 123.456 [various, nan, 123.456]
I am at a complete loss as to why requesting the 'combined' list be made of all columns in the dataframe would create an error, but selecting all but 1 column to create the 'combined' list and the list is created as expected.
Answer
try this :
t['combined']= t.values.tolist()
t
Out[50]:
A B C D combined
0 hello 1 GOOD long.kw [hello, 1, GOOD, long.kw]
1 1.20 chipotle NaN bingo [1.2, chipotle, nan, bingo]
2 various NaN 3000 123.46 [various, nan, 3000, 123.456]