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BUG: Interchange object data buffer has the wrong dtype / from_dataframe incorrect #55227

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Merged
merged 11 commits into from
Nov 7, 2023
Merged

BUG: Interchange object data buffer has the wrong dtype / from_dataframe incorrect #55227

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9876c64
use buffer dtype in interchange from_dataframe
MarcoGorelli Sep 21, 2023
0b936b3
Merge remote-tracking branch 'upstream/main' into use-buffer-dtype-in…
MarcoGorelli Oct 7, 2023
00ad9c7
wip
MarcoGorelli Oct 7, 2023
d54f950
wip
MarcoGorelli Oct 7, 2023
adeceb9
add failing test
MarcoGorelli Oct 7, 2023
3557b4a
wip
MarcoGorelli Oct 10, 2023
975c87c
Merge remote-tracking branch 'upstream/main' into use-buffer-dtype-in…
MarcoGorelli Oct 10, 2023
0ef179a
simplify
MarcoGorelli Oct 10, 2023
df996ac
remove unnecessary assertion
MarcoGorelli Oct 10, 2023
0bea19b
dont double-extract bit width
MarcoGorelli Oct 10, 2023
d04ac92
Update pandas/core/interchange/from_dataframe.py
MarcoGorelli Oct 10, 2023
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16 changes: 8 additions & 8 deletions pandas/core/interchange/from_dataframe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -266,10 +266,9 @@ def string_column_to_ndarray(col: Column) -> tuple[np.ndarray, Any]:

assert buffers["offsets"], "String buffers must contain offsets"
# Retrieve the data buffer containing the UTF-8 code units
data_buff, protocol_data_dtype = buffers["data"]
data_buff, _ = buffers["data"]
# We're going to reinterpret the buffer as uint8, so make sure we can do it safely
assert protocol_data_dtype[1] == 8
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This assertion can indeed be deleted, as we can assume bit width 8 if the column dtype is STRING or LARGE_STRING.

assert protocol_data_dtype[2] in (
assert col.dtype[2] in (
ArrowCTypes.STRING,
ArrowCTypes.LARGE_STRING,
) # format_str == utf-8
Expand Down Expand Up @@ -377,15 +376,16 @@ def datetime_column_to_ndarray(col: Column) -> tuple[np.ndarray | pd.Series, Any
"""
buffers = col.get_buffers()

_, _, format_str, _ = col.dtype
dbuf, dtype = buffers["data"]
_, col_bit_width, format_str, _ = col.dtype
dbuf, _ = buffers["data"]
# Consider dtype being `uint` to get number of units passed since the 01.01.1970

data = buffer_to_ndarray(
dbuf,
(
DtypeKind.UINT,
dtype[1],
getattr(ArrowCTypes, f"UINT{dtype[1]}"),
DtypeKind.INT,
col_bit_width,
getattr(ArrowCTypes, f"INT{col_bit_width}"),
Endianness.NATIVE,
),
offset=col.offset,
Expand Down
22 changes: 22 additions & 0 deletions pandas/tests/interchange/test_impl.py
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Expand Up @@ -14,6 +14,7 @@
DtypeKind,
)
from pandas.core.interchange.from_dataframe import from_dataframe
from pandas.core.interchange.utils import ArrowCTypes


@pytest.fixture
Expand Down Expand Up @@ -326,3 +327,24 @@ def test_interchange_from_non_pandas_tz_aware():
dtype="datetime64[us, Asia/Kathmandu]",
)
tm.assert_frame_equal(expected, result)


def test_interchange_from_corrected_buffer_dtypes(monkeypatch) -> None:
# https://github.com/pandas-dev/pandas/issues/54781
df = pd.DataFrame({"a": ["foo", "bar"]}).__dataframe__()
interchange = df.__dataframe__()
column = interchange.get_column_by_name("a")
buffers = column.get_buffers()
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@WillAyd WillAyd Oct 24, 2023 •
edited
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Not a blocker for this PR but I think these tests would be more impactful if we made the PandasBuffer implement the buffer protocol:

https://docs.cython.org/en/latest/src/userguide/buffer.html

That way we could inspect the bytes for tests

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Started this in #55671

buffers_data = buffers["data"]
buffer_dtype = buffers_data[1]
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Feel free to ignore my possibly wrong commentary as I'm new to this, but I think the offset buffers don't have the proper bufsize here either

(Pdb) buffers["offsets"]
(PandasBuffer({'bufsize': 24, 'ptr': 94440192356160, 'device': 'CPU'}), (<DtypeKind.INT: 0>, 64, 'l', '='))

The standard StringType which inherits from BinaryType in arrow uses a 32 bit offset value, so I think that bufsize should only be 12, unless we are mapping to a LargeString intentionally

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thanks for looking into this - looks like it comes from

pandas/pandas/core/interchange/column.py

Line 364 in d2f05c2

offsets = np.zeros(shape=(len(values) + 1,), dtype=np.int64)

where the dtype's being set to int64. OK to discuss/address this separately?

buffer_dtype = (
DtypeKind.UINT,
8,
ArrowCTypes.UINT8,
buffer_dtype[3],
)
buffers["data"] = (buffers_data[0], buffer_dtype)
column.get_buffers = lambda: buffers
interchange.get_column_by_name = lambda _: column
monkeypatch.setattr(df, "__dataframe__", lambda allow_copy: interchange)
pd.api.interchange.from_dataframe(df)