python_env/lib/site-packages/pandas/tests/interchange/test_utils.py

import numpy as np
import pytest

import pandas as pd
from pandas.core.interchange.utils import dtype_to_arrow_c_fmt

# TODO: use ArrowSchema to get reference C-string.
# At the time, there is no way to access ArrowSchema holding a type format string
# from python. The only way to access it is to export the structure to a C-pointer,
# see DataType._export_to_c() method defined in
# https://github.com/apache/arrow/blob/master/python/pyarrow/types.pxi


@pytest.mark.parametrize(
    "pandas_dtype, c_string",
    [
        (np.dtype("bool"), "b"),
        (np.dtype("int8"), "c"),
        (np.dtype("uint8"), "C"),
        (np.dtype("int16"), "s"),
        (np.dtype("uint16"), "S"),
        (np.dtype("int32"), "i"),
        (np.dtype("uint32"), "I"),
        (np.dtype("int64"), "l"),
        (np.dtype("uint64"), "L"),
        (np.dtype("float16"), "e"),
        (np.dtype("float32"), "f"),
        (np.dtype("float64"), "g"),
        (pd.Series(["a"]).dtype, "u"),
        (
            pd.Series([0]).astype("datetime64[ns]").dtype,
            "tsn:",
        ),
        (pd.CategoricalDtype(["a"]), "l"),
        (np.dtype("O"), "u"),
    ],
)
def test_dtype_to_arrow_c_fmt(pandas_dtype, c_string):  # PR01
    """Test ``dtype_to_arrow_c_fmt`` utility function."""
    assert dtype_to_arrow_c_fmt(pandas_dtype) == c_string


@pytest.mark.parametrize(
    "pa_dtype, args_kwargs, c_string",
    [
        ["null", {}, "n"],
        ["bool_", {}, "b"],
        ["uint8", {}, "C"],
        ["uint16", {}, "S"],
        ["uint32", {}, "I"],
        ["uint64", {}, "L"],
        ["int8", {}, "c"],
        ["int16", {}, "S"],
        ["int32", {}, "i"],
        ["int64", {}, "l"],
        ["float16", {}, "e"],
        ["float32", {}, "f"],
        ["float64", {}, "g"],
        ["string", {}, "u"],
        ["binary", {}, "z"],
        ["time32", ("s",), "tts"],
        ["time32", ("ms",), "ttm"],
        ["time64", ("us",), "ttu"],
        ["time64", ("ns",), "ttn"],
        ["date32", {}, "tdD"],
        ["date64", {}, "tdm"],
        ["timestamp", {"unit": "s"}, "tss:"],
        ["timestamp", {"unit": "ms"}, "tsm:"],
        ["timestamp", {"unit": "us"}, "tsu:"],
        ["timestamp", {"unit": "ns"}, "tsn:"],
        ["timestamp", {"unit": "ns", "tz": "UTC"}, "tsn:UTC"],
        ["duration", ("s",), "tDs"],
        ["duration", ("ms",), "tDm"],
        ["duration", ("us",), "tDu"],
        ["duration", ("ns",), "tDn"],
        ["decimal128", {"precision": 4, "scale": 2}, "d:4,2"],
    ],
)
def test_dtype_to_arrow_c_fmt_arrowdtype(pa_dtype, args_kwargs, c_string):
    # GH 52323
    pa = pytest.importorskip("pyarrow")
    if not args_kwargs:
        pa_type = getattr(pa, pa_dtype)()
    elif isinstance(args_kwargs, tuple):
        pa_type = getattr(pa, pa_dtype)(*args_kwargs)
    else:
        pa_type = getattr(pa, pa_dtype)(**args_kwargs)
    arrow_type = pd.ArrowDtype(pa_type)
    assert dtype_to_arrow_c_fmt(arrow_type) == c_string