polars.api.register_expr_namespace#

polars.api.register_expr_namespace( name: str, ) → Callable[[type[NS]], type[NS]][source]#

Decorator for registering custom functionality with a polars Expr.

Parameters:

name: Name under which the functionality will be accessed.

See also

register_dataframe_namespace: Register functionality on a DataFrame.
register_lazyframe_namespace: Register functionality on a LazyFrame.
register_series_namespace: Register functionality on a Series.

Examples

>>> @pl.api.register_expr_namespace("pow_n")
... class PowersOfN:
...     def __init__(self, expr: pl.Expr):
...         self._expr = expr
...
...     def next(self, p: int) -> pl.Expr:
...         return (p ** (self._expr.log(p).ceil()).cast(pl.Int64)).cast(pl.Int64)
...
...     def previous(self, p: int) -> pl.Expr:
...         return (p ** (self._expr.log(p).floor()).cast(pl.Int64)).cast(pl.Int64)
...
...     def nearest(self, p: int) -> pl.Expr:
...         return (p ** (self._expr.log(p)).round(0).cast(pl.Int64)).cast(pl.Int64)
...
>>>
>>> df = pl.DataFrame([1.4, 24.3, 55.0, 64.001], schema=["n"])
>>> df.select(
...     pl.col("n"),
...     pl.col("n").pow_n.next(p=2).alias("next_pow2"),
...     pl.col("n").pow_n.previous(p=2).alias("prev_pow2"),
...     pl.col("n").pow_n.nearest(p=2).alias("nearest_pow2"),
... )
shape: (4, 4)
┌────────┬───────────┬───────────┬──────────────┐
│ n      ┆ next_pow2 ┆ prev_pow2 ┆ nearest_pow2 │
│ ---    ┆ ---       ┆ ---       ┆ ---          │
│ f64    ┆ i64       ┆ i64       ┆ i64          │
╞════════╪═══════════╪═══════════╪══════════════╡
│ 1.4    ┆ 2         ┆ 1         ┆ 1            │
│ 24.3   ┆ 32        ┆ 16        ┆ 32           │
│ 55.0   ┆ 64        ┆ 32        ┆ 64           │
│ 64.001 ┆ 128       ┆ 64        ┆ 64           │
└────────┴───────────┴───────────┴──────────────┘