140 lines
5.4 KiB
Python
140 lines
5.4 KiB
Python
from __future__ import annotations
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from typing import TYPE_CHECKING, Any
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from narwhals._pandas_like.utils import select_columns_by_name
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from narwhals._utils import Implementation, Version, isinstance_or_issubclass
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from narwhals.dependencies import get_pyarrow
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if TYPE_CHECKING:
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from collections.abc import Mapping, Sequence
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import dask.dataframe as dd
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import dask.dataframe.dask_expr as dx
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from narwhals._dask.dataframe import DaskLazyFrame, Incomplete
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from narwhals._dask.expr import DaskExpr
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from narwhals.dtypes import DType
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from narwhals.typing import IntoDType
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else:
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try:
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import dask.dataframe.dask_expr as dx
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except ModuleNotFoundError: # pragma: no cover
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import dask_expr as dx
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def maybe_evaluate_expr(df: DaskLazyFrame, obj: DaskExpr | object) -> dx.Series | object:
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from narwhals._dask.expr import DaskExpr
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if isinstance(obj, DaskExpr):
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results = obj._call(df)
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assert len(results) == 1 # debug assertion # noqa: S101
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return results[0]
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return obj
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def evaluate_exprs(df: DaskLazyFrame, /, *exprs: DaskExpr) -> list[tuple[str, dx.Series]]:
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native_results: list[tuple[str, dx.Series]] = []
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for expr in exprs:
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native_series_list = expr(df)
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aliases = expr._evaluate_aliases(df)
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if len(aliases) != len(native_series_list): # pragma: no cover
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msg = f"Internal error: got aliases {aliases}, but only got {len(native_series_list)} results"
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raise AssertionError(msg)
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native_results.extend(zip(aliases, native_series_list))
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return native_results
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def align_series_full_broadcast(
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df: DaskLazyFrame, *series: dx.Series | object
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) -> Sequence[dx.Series]:
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return [
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s if isinstance(s, dx.Series) else df._native_frame.assign(_tmp=s)["_tmp"]
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for s in series
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] # pyright: ignore[reportReturnType]
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def add_row_index(frame: dd.DataFrame, name: str) -> dd.DataFrame:
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original_cols = frame.columns
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df: Incomplete = frame.assign(**{name: 1})
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return select_columns_by_name(
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df.assign(**{name: df[name].cumsum(method="blelloch") - 1}),
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[name, *original_cols],
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Implementation.DASK,
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)
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def validate_comparand(lhs: dx.Series, rhs: dx.Series) -> None:
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if not dx.expr.are_co_aligned(lhs._expr, rhs._expr): # pragma: no cover
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# are_co_aligned is a method which cheaply checks if two Dask expressions
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# have the same index, and therefore don't require index alignment.
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# If someone only operates on a Dask DataFrame via expressions, then this
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# should always be the case: expression outputs (by definition) all come from the
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# same input dataframe, and Dask Series does not have any operations which
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# change the index. Nonetheless, we perform this safety check anyway.
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# However, we still need to carefully vet which methods we support for Dask, to
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# avoid issues where `are_co_aligned` doesn't do what we want it to do:
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# https://github.com/dask/dask-expr/issues/1112.
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msg = "Objects are not co-aligned, so this operation is not supported for Dask backend"
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raise RuntimeError(msg)
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dtypes = Version.MAIN.dtypes
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dtypes_v1 = Version.V1.dtypes
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NW_TO_DASK_DTYPES: Mapping[type[DType], str] = {
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dtypes.Float64: "float64",
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dtypes.Float32: "float32",
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dtypes.Boolean: "bool",
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dtypes.Categorical: "category",
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dtypes.Date: "date32[day][pyarrow]",
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dtypes.Int8: "int8",
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dtypes.Int16: "int16",
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dtypes.Int32: "int32",
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dtypes.Int64: "int64",
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dtypes.UInt8: "uint8",
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dtypes.UInt16: "uint16",
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dtypes.UInt32: "uint32",
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dtypes.UInt64: "uint64",
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dtypes.Datetime: "datetime64[us]",
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dtypes.Duration: "timedelta64[ns]",
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dtypes_v1.Datetime: "datetime64[us]",
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dtypes_v1.Duration: "timedelta64[ns]",
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}
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UNSUPPORTED_DTYPES = (
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dtypes.List,
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dtypes.Struct,
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dtypes.Array,
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dtypes.Time,
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dtypes.Binary,
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)
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def narwhals_to_native_dtype(dtype: IntoDType, version: Version) -> Any:
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dtypes = version.dtypes
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base_type = dtype.base_type()
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if dask_type := NW_TO_DASK_DTYPES.get(base_type):
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return dask_type
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if isinstance_or_issubclass(dtype, dtypes.String):
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if Implementation.PANDAS._backend_version() >= (2, 0, 0):
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return "string[pyarrow]" if get_pyarrow() else "string[python]"
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return "object" # pragma: no cover
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if isinstance_or_issubclass(dtype, dtypes.Enum):
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if version is Version.V1:
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msg = "Converting to Enum is not supported in narwhals.stable.v1"
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raise NotImplementedError(msg)
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if isinstance(dtype, dtypes.Enum):
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import pandas as pd
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# NOTE: `pandas-stubs.core.dtypes.dtypes.CategoricalDtype.categories` is too narrow
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# Should be one of the `ListLike*` types
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# https://github.com/pandas-dev/pandas-stubs/blob/8434bde95460b996323cc8c0fea7b0a8bb00ea26/pandas-stubs/_typing.pyi#L497-L505
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return pd.CategoricalDtype(dtype.categories, ordered=True) # type: ignore[arg-type]
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msg = "Can not cast / initialize Enum without categories present"
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raise ValueError(msg)
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if issubclass(base_type, UNSUPPORTED_DTYPES): # pragma: no cover
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msg = f"Converting to {base_type.__name__} dtype is not supported for Dask."
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raise NotImplementedError(msg)
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msg = f"Unknown dtype: {dtype}" # pragma: no cover
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raise AssertionError(msg)
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