Implement base MissingValues strategies

frontend/mvstrategy.py

@@ -0,0 +1,70 @@
+from abc import ABC, abstractmethod
+from pandas import DataFrame, Series
+from pandas.api.types import is_numeric_dtype
+from typing import Any, Union
+
+class MVStrategy(ABC):
+    """A way to handle missing values in a dataframe."""
+
+    @abstractmethod
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        """Apply the current strategy to the given series.
+
+        The series is described by its label and dataframe."""
+        return df
+
+    @staticmethod
+    def list_available(series: Series) -> list['MVStrategy']:
+        """Get all the strategies that can be used."""
+        choices = [DropStrategy(), ModeStrategy()]
+        if is_numeric_dtype(series):
+            choices.extend((MeanStrategy(), MedianStrategy()))
+        return choices
+
+
+class DropStrategy(MVStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        df.dropna(subset=label, inplace=True)
+        return df
+
+    def __str__(self) -> str:
+        return "Drop"
+
+
+class PositionStrategy(MVStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        series.fillna(self.get_value(series), inplace=True)
+        return df
+
+    @abstractmethod
+    def get_value(self, series: Series) -> Any:
+        pass
+
+
+class MeanStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Union[int, float]:
+        return series.mean()
+
+    def __str__(self) -> str:
+        return "Use mean"
+
+
+class MedianStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Union[int, float]:
+        return series.median()
+
+    def __str__(self) -> str:
+        return "Use median"
+
+
+class ModeStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Any:
+        return series.mode()[0]
+
+    def __str__(self) -> str:
+        return "Use mode"