Parity in methods between `polars.Series` and `polars.Expr`

[wangkev]

Parity in methods between `polars.Series` and `polars.Expr`

[ritchie46]

Expression and Series have a different goal. It isn't encouraged to do data processing with Series. They are a mere data structure that help you get some insight in a final materialized result.

Doing data processing on Series instead of on expressions is very very bad. This will allow now optimizations, late materializations and have no benefit from the query engine.

Having full parity is therefore not a goal and processing on a pure Series is discouraged.

[wangkev]

Understand where you're coming from regarding the performance considerations of using Series and that its usage should be discouraged in favor of expressions. Although, I also think that without having parity, it leaves Series in a weird place, almost as an afterthought -- a bit unclear on its intended usage and differences with expressions. It has kind of the same logical meaning as expressions. It has some of the features, but not all. And its not clear when we can delegate to series or when we need to do the processing on Dataframe/expressions.