Aggregation

Expr.agg_groups()	Get the group indexes of the group by operation.
Expr.arg_max()	Get the index of the maximal value.
Expr.arg_min()	Get the index of the minimal value.
Expr.count()	Return the number of non-null elements in the column.
Expr.first()	Get the first value.
Expr.implode()	Aggregate values into a list.
Expr.last()	Get the last value.
Expr.len()	Return the number of elements in the column.
Expr.max()	Get maximum value.
Expr.mean()	Get mean value.
Expr.median()	Get median value using linear interpolation.
Expr.min()	Get minimum value.
Expr.nan_max()	Get maximum value, but propagate/poison encountered NaN values.
Expr.nan_min()	Get minimum value, but propagate/poison encountered NaN values.
Expr.product()	Compute the product of an expression.
Expr.quantile(quantile[, interpolation])	Get quantile value.
Expr.std([ddof])	Get standard deviation.
Expr.sum()	Get sum value.
Expr.var([ddof])	Get variance.