Polars

Polars is the fast successor to Pandas. Written in Rust, query-optimized, and parallelized. v1.0 (2024) signaled production readiness.

When to Use

• Performance: 10-100x faster than Pandas on large data.
• Lazy Evaluation: Define a query plan and execute it efficiently (.collect()).
• Streaming: Process datasets larger than RAM.

Core Concepts

Lazy API (.lazy())

Builds a query plan. Polars optimizes it (predicate pushdown) before reducing it.

Expressions

pl.col("a").sum() is an expression, not a direct calculation.

Compatibility

Can convert to/from Pandas/PyArrow zero-copy.

Best Practices (2025)

Do:

• Use Lazy Mode: df.lazy().filter(...).collect().
• Use scan_parquet: Don't load the whole file; scan it.
• Use GPU engine: Polars has experimental NVIDIA RAPIDS support.

Don't:

• Don't treat it like Pandas: The API is different (axis=1 doesn't exist; use expressions).

References

• Polars Documentation