Replacing each Null value in dataframe with a list

Question

I am trying to replace each instance of null value by a different value each time. The values are in a list CB.

import pandas as pd
import numpy as np
df = pd.Dat         


        

Answer 1

Let's say we have a dataframe (making it a bit bigger that the original question)

df = pd.read_csv(StringIO(
"""
   a   b   c   d
0  0   4   5   6
1  0 NaN NaN NaN
"""), delim_whitespace=True)

then we can do the following

dfs = df.stack(dropna = False)
dfs[dfs.isna()] = CB
df = dfs.unstack()
df

produces

    a   b   c   d
0   0.0 4.0 5.0 6.0
1   0.0 1.0 2.0 3.0

Here we unwrap the df into a timeseries using stack(), filter to NaNs, replace with CB, and fold back into the original shape