8000 feat: add `cast` to DataFrame by ion-elgreco · Pull Request #916 · apache/datafusion-python · GitHub
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feat: add cast to DataFrame #916

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Merged
merged 4 commits into from
Oct 21, 2024
Merged

feat: add cast to DataFrame #916

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35656f1
feat: add with_columns
ion-elgreco Oct 12, 2024
bded1c4
feat: add top level cast
ion-elgreco Oct 13, 2024
b39a5f0
chore: improve docstring
ion-elgreco Oct 13, 2024
c698c97
Merge branch 'main' into feat--cast-dataframe
timsaucer Oct 21, 2024
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13 changes: 13 additions & 0 deletions python/datafusion/dataframe.py
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Expand Up @@ -21,6 +21,7 @@

from __future__ import annotations


from typing import Any, Iterable, List, Literal, TYPE_CHECKING
from datafusion.record_batch import RecordBatchStream
from typing_extensions import deprecated
Expand Down Expand Up @@ -267,6 +268,18 @@ def sort(self, *exprs: Expr | SortExpr) -> DataFrame:
exprs_raw = [sort_or_default(expr) for expr in exprs]
return DataFrame(self.df.sort(*exprs_raw))

def cast(self, mapping: dict[str, pa.DataType[Any]]) -> DataFrame:
"""Cast one or more columns to a different data type.

Args:
mapping: Mapped with column as key and column dtype as value.

Returns:
DataFrame after casting columns
"""
exprs = [Expr.column(col).cast(dtype) for col, dtype in mapping.items()]
return self.with_columns(exprs)

def limit(self, count: int, offset: int = 0) -> DataFrame:
"""Return a new :py:class:`DataFrame` with a limited number of rows.

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9 changes: 9 additions & 0 deletions python/tests/test_dataframe.py
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Expand Up @@ -247,6 +247,15 @@ def test_with_columns(df):
assert result.column(6) == pa.array([5, 7, 9])


def test_cast(df):
df = df.cast({"a": pa.float16(), "b": pa.list_(pa.uint32())})
expected = pa.schema(
[("a", pa.float16()), ("b", pa.list_(pa.uint32())), ("c", pa.int64())]
)

assert df.schema() == expected


def test_with_column_renamed(df):
df = df.with_column("c", column("a") + column("b")).with_column_renamed("c", "sum")

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