The library pandas are mainly used for data manipulation. For importing-
import pandas as pd
For filling up missing values based on mean,median or mode of a dataset, there is a term called imputer in scikit-learn library. For using-
from sklearn.impute import SimpleImputer
After that, filling up the missing data based on mean-
imputer = SimpleImputer(missing_values=np.nan, strategy='mean')
Based on median-
imputer = SimpleImputer(missing_values=np.nan, strategy='median')
Based on mode-
imputer = SimpleImputer(missing_values=np.nan, strategy='most_frequent')
For transfarring string value to numerical value-
from sklearn.preprocessing import LabelEncoder
labelEncoder_X = LabelEncoder()
X.iloc[:,0] = labelEncoder_X.fit_transform(X.iloc[:,0])