patito.Relation

Relation.__init__(derived_from, database=None, model=None)

Create a new relation object containing data to be queried with DuckDB.

Parameters

  • derived_from (Union[DataFrame, DataFrame, DataFrame, Path, str, DuckDBPyRelation, Relation]) –

    Data to be represented as a DuckDB relation object. Can be one of the following types:

    • A pandas or polars DataFrame.

    • An SQL query represented as a string.

    • A Path object pointing to a CSV or a parquet file. The path must point to an existing file with either a .csv or .parquet file extension.

    • A native DuckDB relation object (duckdb.DuckDBPyRelation).

    • A patito.Relation object.

  • database (Optional[Database]) – Which database to load the relation into. If not provided, the default DuckDB database will be used.

  • model (Optional[Type[TypeVar(ModelType, bound= Model)]]) –

    Sub-class of patito.Model which specifies how to deserialize rows when fetched with methods such as Relation.get() and __iter__().

    Will also be used to create a strict table schema if Relation.create_table(). schema should be constructed.

    If not provided, a dynamic model fitting the relation schema will be created when required.

    Can also be set later dynamically by invoking Relation.set_model().

Raises

  • ValueError – If any one of the following cases are encountered: - If a provided Path object does not have a .csv or .parquet file extension. - If a database and relation object is provided, but the relation object does not belong to the database.

  • TypeError – If the type of derived_from is not supported.

Examples

Instantiated from a dataframe:

>>> import patito as pt
>>> df = pt.DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
>>> pt.Relation(df).filter("a > 2").to_df()
shape: (1, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 3   ┆ 6   │
└─────┴─────┘

Instantiated from an SQL query:

>>> pt.Relation("select 1 as a, 2 as b").to_df()
shape: (1, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 1   ┆ 2   │
└─────┴─────┘

Properties

Methods