Pandas fillna vs scikit-learn SimpleImputer

Both pandas and scikit-learn provide tools for dealing with missing data. Pandas offers a "fillna" functionality that can perform univariate imputations as well as more advanced tasks such as working with dates and forward/backward filling. In comparison, scikit-learn's SimpleImputer only offers basic functionality for filling missing values and does not have the same advanced features as pandas. There are some specific considerations to be aware of when using these tools, such as the behavior of backfilling and forward filling methods.