change NaN value on a specific column code example

Example 1: replace nan in pandas column with mode and printing it

def exercise4(df):
    df1 = df.select_dtypes(np.number)
    df2 = df.select_dtypes(exclude = 'float')
    mode = df2.mode()
    df3 = df1.fillna(df.mean())
    df4 = df2.fillna(mode.iloc[0,:])
    new_df = [df3,df4]
    df5 = pd.concat(new_df,axis=1)
    new_cols = list(df.columns)
    df6 = df5[new_cols]
    return df6

Example 2: pandas replace nan with value above

>>> df = pd.DataFrame([[1, 2, 3], [4, None, None], [None, None, 9]])
>>> df.fillna(method='ffill')
   0  1  2
0  1  2  3
1  4  2  3
2  4  2  9