How to append a numpy array to a pandas dataframe

Question

I'm trying to append a 3x2 numpy array to an existing dataframe. Something like this:

import pandas as pd
import numpy as np
df = pd.Dataframe({"A": [0,0,0], "B": [1,1,1]})
arr = np.arange(6).reshape(3, 2)

df[["C", "D"]] = arr  # NOPE!

How do I get this to work?

Erfan · Accepted Answer · 2019-06-22 12:53:29Z

5

Use concat while converting your array to a dataframe:

df = pd.concat([df, pd.DataFrame(arr, columns=["C", "D"])], axis=1)

   A  B  C  D
0  0  1  0  1
1  0  1  2  3
2  0  1  4  5

answered Jun 22, 2019 at 12:53

Erfan

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Comments

Francesco Zambolin · Accepted Answer · 2019-06-22 13:01:13Z

0

It didn't work because you need to pass a df:

arr = pd.DataFrame(np.arange(6).reshape(3, 2))

df[["C", "D"]] = arr #YEP

#Output
    A   B   C   D

0   0   1   0   1

1   0   1   2   3

2   0   1   4   5

answered Jun 22, 2019 at 13:01

Francesco Zambolin

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