polars.api.register_dataframe_namespace

polars.api.register_dataframe_namespace(

name: str,

) → Callable[[type[NS]], type[NS]]

Decorator for registering custom functionality with a polars DataFrame.

Parameters:

name

Name under which the functionality will be accessed.

See also

register_expr_namespace

Register functionality on an Expr.

register_lazyframe_namespace

Register functionality on a LazyFrame.

register_series_namespace

Register functionality on a Series.

Examples

>>> @pl.api.register_dataframe_namespace("split")
... class SplitFrame:
...     def __init__(self, df: pl.DataFrame):
...         self._df = df
...
...     def by_first_letter_of_column_names(self) -> list[pl.DataFrame]:
...         return [
...             self._df.select([col for col in self._df.columns if col[0] == f])
...             for f in dict.fromkeys(col[0] for col in self._df.columns)
...         ]
...
...     def by_first_letter_of_column_values(self, col: str) -> list[pl.DataFrame]:
...         return [
...             self._df.filter(pl.col(col).str.starts_with(c))
...             for c in sorted(
...                 set(df.select(pl.col(col).str.slice(0, 1)).to_series())
...             )
...         ]
...
>>>
>>> df = pl.DataFrame(
...     data=[["xx", 2, 3, 4], ["xy", 4, 5, 6], ["yy", 5, 6, 7], ["yz", 6, 7, 8]],
...     schema=["a1", "a2", "b1", "b2"],
...     orient="row",
... )
>>> df
shape: (4, 4)
┌─────┬─────┬─────┬─────┐
│ a1  ┆ a2  ┆ b1  ┆ b2  │
│ --- ┆ --- ┆ --- ┆ --- │
│ str ┆ i64 ┆ i64 ┆ i64 │
╞═════╪═════╪═════╪═════╡
│ xx  ┆ 2   ┆ 3   ┆ 4   │
│ xy  ┆ 4   ┆ 5   ┆ 6   │
│ yy  ┆ 5   ┆ 6   ┆ 7   │
│ yz  ┆ 6   ┆ 7   ┆ 8   │
└─────┴─────┴─────┴─────┘
>>> df.split.by_first_letter_of_column_names()
[shape: (4, 2)
┌─────┬─────┐
│ a1  ┆ a2  │
│ --- ┆ --- │
│ str ┆ i64 │
╞═════╪═════╡
│ xx  ┆ 2   │
│ xy  ┆ 4   │
│ yy  ┆ 5   │
│ yz  ┆ 6   │
└─────┴─────┘,
shape: (4, 2)
┌─────┬─────┐
│ b1  ┆ b2  │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 3   ┆ 4   │
│ 5   ┆ 6   │
│ 6   ┆ 7   │
│ 7   ┆ 8   │
└─────┴─────┘]
>>> df.split.by_first_letter_of_column_values("a1")
[shape: (2, 4)
┌─────┬─────┬─────┬─────┐
│ a1  ┆ a2  ┆ b1  ┆ b2  │
│ --- ┆ --- ┆ --- ┆ --- │
│ str ┆ i64 ┆ i64 ┆ i64 │
╞═════╪═════╪═════╪═════╡
│ xx  ┆ 2   ┆ 3   ┆ 4   │
│ xy  ┆ 4   ┆ 5   ┆ 6   │
└─────┴─────┴─────┴─────┘, shape: (2, 4)
┌─────┬─────┬─────┬─────┐
│ a1  ┆ a2  ┆ b1  ┆ b2  │
│ --- ┆ --- ┆ --- ┆ --- │
│ str ┆ i64 ┆ i64 ┆ i64 │
╞═════╪═════╪═════╪═════╡
│ yy  ┆ 5   ┆ 6   ┆ 7   │
│ yz  ┆ 6   ┆ 7   ┆ 8   │
└─────┴─────┴─────┴─────┘]