DataFrameMethod

laktory.models.dataframe.DataFrameMethod

Bases: BaseModel, PipelineChild

Definition of a DataFrame method to be applied. Both native and Narwhals API are supported.

Examples:

import polars as pl

import laktory as lk

df0 = pl.DataFrame(
    {
        "x": [1.1, 2.2, 3.3],
    }
)

m1 = lk.models.DataFrameMethod(
    func_name="with_columns",
    func_kwargs={"xr": "nw.col('x').round()"},
    dataframe_api="NARWHALS",
)
df = m1.execute(df0)

m2 = lk.models.DataFrameMethod(
    func_name="select", func_args=["pl.col('x').sqrt()"], dataframe_api="NATIVE"
)
df = m2.execute(df0)

print(df.to_native())
'''
| x        |
|----------|
| 1.048809 |
| 1.48324  |
| 1.81659  |
'''

PARAMETER	DESCRIPTION
func_args	Arguments passed to method. A DataSource model can be passed instead of a DataFrame. TYPE: list[DataFrameMethodArg | Any | VariableType] | VariableType DEFAULT: []
func_kwargs	Keyword arguments passed to method. A DataSource model can be passed instead of a DataFrame. TYPE: dict[str | VariableType, DataFrameMethodArg | Any | VariableType] | VariableType DEFAULT: {}
func_name	DataFrame method or attribute name (e.g. 'select', 'filter', 'dt.strftime'). Resolved as an attribute of the DataFrame object. TYPE: str | VariableType

METHOD	DESCRIPTION
execute	Execute method on provided DataFrame df.

ATTRIBUTE	DESCRIPTION
data_sources	Get all sources feeding the DataFrame Method TYPE: list[DataSourcesUnion]
upstream_node_names	Pipeline node names required to apply transformer node. TYPE: list[str]

data_sources property

Get all sources feeding the DataFrame Method

upstream_node_names property

Pipeline node names required to apply transformer node.

execute(df)

Execute method on provided DataFrame df.

PARAMETER	DESCRIPTION
df	Input dataframe TYPE: AnyFrame

RETURNS	DESCRIPTION
Output dataframe

Source code in laktory/models/dataframe/dataframemethod.py

def execute(self, df: AnyFrame) -> Union[AnyFrame]:
    """
    Execute method on provided DataFrame `df`.

    Parameters
    ----------
    df:
        Input dataframe

    Returns
    -------
        Output dataframe
    """

    # Get and set Backend (required to evaluate arguments)
    backend = DataFrameBackends.from_df(df)
    self.dataframe_backend_ = backend

    # Convert to Narwhals
    if not isinstance(df, AnyFrame):
        df = nw.from_native(df)
    if self.dataframe_api == "NATIVE":
        df = df.to_native()

    # Get Function
    namespace = None
    func_name = self.func_name
    func_full_name = func_name
    if "." in func_name:
        namespace, func_name = func_name.split(".")
    df_as_input = False

    # Get from built-in narwhals and narwhals extension (including Laktory) functions
    f = None
    if f is None:
        # Get function from namespace extension
        if namespace:
            f = getattr(getattr(df, namespace), func_name, None)
        else:
            f = getattr(df, func_name, None)

    if f is None:
        df_type = type(df)
        raise ValueError(
            f"Function {func_full_name} is not available on dataframe of type {str(df_type)} with {self.dataframe_api} API"
        )

    _args = self.func_args
    _kwargs = self.func_kwargs

    # Build log
    func_log = f"df.{func_full_name}("
    func_log += ",".join([a.signature() for a in _args])
    func_log += ",".join([f"{k}={a.signature()}" for k, a in _kwargs.items()])
    func_log += f") with df type {type(df)}"
    logger.info(f"Applying {func_log}")

    # Build args
    args = []
    if df_as_input:
        args += [df]
    for i, _arg in enumerate(_args):
        args += [_arg.eval(backend=backend)]

    # Build kwargs
    kwargs = {}
    for k, _arg in _kwargs.items():
        kwargs[k] = _arg.eval(backend=backend)

    # Inject laktory_context if the function accepts it
    from laktory.models.laktorycontext import LaktoryContext
    from laktory.models.laktorycontext import _build_laktory_context_kwargs

    context = LaktoryContext(
        node=self.parent_pipeline_node,
        pipeline=self.parent_pipeline,
    )
    kwargs.update(_build_laktory_context_kwargs(f, context))

    # Call function
    df = f(*args, **kwargs)

    # Convert to narwhals when custom function don't return a Narwhals DataFrame
    if not isinstance(df, AnyFrame):
        df = nw.from_native(df)

    return df