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Reproducible Example

import pandas as pd
import numpy as np

df = pd.DataFrame({'col1': ['5', 0, np.NaN, 10, np.NaN],
        'col2': [7, np.NaN, np.NaN, 5, 3],
        'col3': [12, np.NaN, 1, 2, 0],
        'col4': [np.NaN, 1, 1, np.NaN, 18]})

  col1  col2  col3  col4
0    5   7.0  12.0   NaN
1    0   NaN   NaN   1.0
2  NaN   NaN   1.0   1.0
3   10   5.0   2.0   NaN
4  NaN   3.0   0.0  18.0

Issue Description

The following code does not appear to give the correct results. It appears that the axis parameter is ignored.

df.fillna(50,limit=1,axis=1)

   col1  col2  col3  col4
0   5.0   7.0  12.0  50.0
1   0.0  50.0  50.0   1.0
2  50.0   NaN   1.0   1.0
3  10.0   5.0   2.0   NaN
4   NaN   3.0   0.0  18.0

However, if just one value in the df is a string value, it appears to work correctly. I have made the first value in the dataframe a string value.

df = pd.DataFrame({'col1': ['5', 0, np.NaN, 10, np.NaN], 'col2': [7, np.NaN, np.NaN, 5, 3], 'col3': [12, np.NaN, 1, 2, 0], 'col4': [np.NaN, 1, 1, np.NaN, 18]})

using the same code as above, it now appears that the axis parameter is not ignored.

df.fillna(50,limit=1,axis=1)

   col1  col2  col3  col4
0     5   7.0  12.0    50
1   0.0  50.0   NaN   1.0
2  50.0   NaN   1.0   1.0
3  10.0   5.0   2.0  50.0
4  50.0   3.0   0.0  18.0

Expected Behavior

fillna() should not ignore the axis parameter, and each NaN value should be filled with 50 along axis = 1

Installed Versions