Python Pandas: Assign numpy array to a part of dataframe

Question

lets say I have a dataframe like this:

 A    B     C 
 1   NaN   NaN 
 2   NaN   NaN

And I have a numpy array like this np_array = ['ab', 'bc'], I want to make this array as a part of the dataframe rows like this:

 A    B      C 
 1   'ab'   'bc'
 2   NaN     NaN

How can I do this most efficiently. Thanks=)

or maybe: df.fillna({c:v for c,v in zip(df.columns, np_array)}, limit=1) — gbruenjes
– gbruenjes, Commented Mar 13, 2020 at 8:45

Chetan Ameta · Accepted Answer · 2020-03-13 09:10:01Z

1

Try below solution:

import pandas as pd
import numpy as np

dic = {'A': [1, 2], 'B': [None, None], 'C': [None, None]}
np_array = np.array(['ab', 'bc'])
df = pd.DataFrame(dic)

print(df)

#Method 1
df.iloc[0, 1:] = np_array
print(df)

#Medthod 2

df = pd.DataFrame(dic)
df.loc[0, ['B', 'C']] = np_array
print(df)

Output

   A     B     C
0  1  None  None
1  2  None  None

   A     B     C
0  1    ab    bc
1  2  None  None

Name: 0, dtype: object

   A     B     C
0  1    ab    bc
1  2  None  None

answered Mar 13, 2020 at 9:10

Chetan Ameta

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Comments

Sam · Accepted Answer · 2020-03-13 08:51:43Z

0

This can be done with:

df.iloc[row] = np_array

where row is the 0-indexed row you want to change

answered Mar 13, 2020 at 8:51

Sam

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