PYTHON

Replace the string with NAN value

data['horsepower'].replace(to_replace='?' , value = np.nan,inplace = True)
data['horsepower'].unique()

pandas replace nan with mean

--fillna
product_mean = df['product'].mean()
df['product'] = df['product'].fillna(product_mean)

--replace method
col_mean = np.mean(df['col'])
df['col'] = df['col'].replace(np.nan, col_mean)

replace nan

df['salary'] = df['salary'].fillna(df['salary'].mode()[0])

Replace NaN value by mean of all column

data.loc[data['taille'].isnull(), 'taille'] = data['taille'].mean()