There are two common strategies. Omission and Imputation. Omission refers to removing rows or columns with missing values, while imputation refers to adding values to fill in missing observations.
There are some helpful modules in Scikit-learn that you can use for imputation. One is SimpleImputer which fills missing values with a zero, or the median, mean, or mode, while IterativeImputer models each feature with missing values as a function of other features.
